I'm working on modernizing Rosetta Code's infrastructure. Starting with communications. Please accept this time-limited open invite to RC's Slack.. --Michael Mol (talk) 20:59, 30 May 2020 (UTC)

Strange unique prime triplets

From Rosetta Code
Strange unique prime triplets is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Primes   n,   m,   and   p   are   strange unique primes   if   n,   m,   and   p   are unique and their sum     n + m + p     is also prime. Assume n < m < p.


Task
  •   Find all triplets of strange unique primes in which   n,   m,   and   p   are all less than   30.
  •   (stretch goal)   Show the count (only) of all the triplets of strange unique primes in which     n, m, and p    are all less than   1,000.



11l[edit]

Translation of: Python
F primes_upto(limit)
V is_prime = [0B] * 2 [+] [1B] * (limit - 1)
L(n) 0 .< Int(limit ^ 0.5 + 1.5)
I is_prime[n]
L(i) (n * n .< limit + 1).step(n)
is_prime[i] = 0B
R enumerate(is_prime).filter((i, prime) -> prime).map((i, prime) -> i)
 
F strange_triplets(Int mx = 30)
[(Int, Int, Int)] r
V primes = Array(primes_upto(mx))
V primes3 = Set(primes_upto(3 * mx))
L(n) primes
V i = L.index
L(m) primes[i + 1 ..]
V j = L.index + i + 1
L(p) primes[j + 1 ..]
I n + m + p C primes3
r.append((n, m, p))
R r
 
L(n, m, p) strange_triplets()
print(‘#2: #2+#2+#2 = #.’.format(L.index + 1, n, m, p, n + m + p))
 
V mx = 1'000
print("\nIf n, m, p < #. finds #.".format(mx, strange_triplets(mx).len))
Output:
 1:  3+ 5+11 = 19
 2:  3+ 5+23 = 31
 3:  3+ 5+29 = 37
 4:  3+ 7+13 = 23
 5:  3+ 7+19 = 29
 6:  3+11+17 = 31
 7:  3+11+23 = 37
 8:  3+11+29 = 43
 9:  3+17+23 = 43
10:  5+ 7+11 = 23
11:  5+ 7+17 = 29
12:  5+ 7+19 = 31
13:  5+ 7+29 = 41
14:  5+11+13 = 29
15:  5+13+19 = 37
16:  5+13+23 = 41
17:  5+13+29 = 47
18:  5+17+19 = 41
19:  5+19+23 = 47
20:  5+19+29 = 53
21:  7+11+13 = 31
22:  7+11+19 = 37
23:  7+11+23 = 41
24:  7+11+29 = 47
25:  7+13+17 = 37
26:  7+13+23 = 43
27:  7+17+19 = 43
28:  7+17+23 = 47
29:  7+17+29 = 53
30:  7+23+29 = 59
31: 11+13+17 = 41
32: 11+13+19 = 43
33: 11+13+23 = 47
34: 11+13+29 = 53
35: 11+17+19 = 47
36: 11+19+23 = 53
37: 11+19+29 = 59
38: 13+17+23 = 53
39: 13+17+29 = 59
40: 13+19+29 = 61
41: 17+19+23 = 59
42: 19+23+29 = 71

If n, m, p < 1000 finds 241580

Action![edit]

INCLUDE "H6:SIEVE.ACT"
 
PROC Main()
DEFINE MAXPRIME="29"
DEFINE MAX="99"
BYTE ARRAY primes(MAX+1)
BYTE n,m,p,c
INT count=[0]
 
Put(125) PutE() ;clear the screen
Sieve(primes,MAX+1)
c=0
FOR n=2 TO MAXPRIME-2
DO
IF primes(n) THEN
FOR m=n+1 TO MAXPRIME-1
DO
IF primes(m) THEN
FOR p=m+1 TO MAXPRIME
DO
IF primes(p)=1 AND primes(n+m+p)=1 THEN
PrintF("%I+%I+%I=%I ",n,m,p,n+m+p)
count==+1 c==+1
IF c=3 THEN
c=0 PutE()
FI
FI
OD
FI
OD
FI
OD
PrintF("%EThere are %I prime triplets",count)
RETURN
Output:

Screenshot from Atari 8-bit computer

3+5+11=19 3+5+23=31 3+5+29=37
3+7+13=23 3+7+19=29 3+11+17=31
3+11+23=37 3+11+29=43 3+17+23=43
5+7+11=23 5+7+17=29 5+7+19=31
5+7+29=41 5+11+13=29 5+13+19=37
5+13+23=41 5+13+29=47 5+17+19=41
5+19+23=47 5+19+29=53 7+11+13=31
7+11+19=37 7+11+23=41 7+11+29=47
7+13+17=37 7+13+23=43 7+17+19=43
7+17+23=47 7+17+29=53 7+23+29=59
11+13+17=41 11+13+19=43 11+13+23=47
11+13+29=53 11+17+19=47 11+19+23=53
11+19+29=59 13+17+23=53 13+17+29=59
13+19+29=61 17+19+23=59 19+23+29=71

There are 42 prime triplets

ALGOL 68[edit]

Translation of: Algol W
which is based on
Translation of: Wren
BEGIN # find some strange unique primes - triplets of primes n, m, p        #
# where n + m + p is also prime and n =/= m =/= p #
# we need to find the strange unique prime triplets below 1000 #
# so the maximum triplet sum could be roughly 3000 #
INT max number = 1000;
# sieve the primes to the maximum reuired prime #
PR read "primes.incl.a68" PR
[]BOOL prime = PRIMESIEVE ( max number * 3 );
# we need to find the strange unique prime triplets below 1000 #
INT s count := 0, c30 := 0;
# 2 cannot be one of the primes as the sum would be even otherwise #
FOR n FROM 3 BY 2 TO max number - 5 DO
IF prime[ n ] THEN
FOR m FROM n + 2 BY 2 TO max number- 3 DO
IF prime[ m ] THEN
FOR p FROM m + 2 BY 2 TO max number DO
IF prime[ p ] THEN
IF INT s = n + m + p;
prime[ s ]
THEN
# have 3 unique primes whose sum is prime #
s count +:= 1;
IF p <= 30 AND m <= 30 AND n <= 30 THEN
c30 +:= 1;
print( ( whole( c30, -3 ), ": "
, whole( n, -3 ), " + "
, whole( m, -3 ), " + "
, whole( p, -3 ), " = "
, whole( s, -3 ), newline
)
)
FI
FI
FI
OD # p #
FI
OD # m #
FI
OD # n # ;
print( ( "Found ", whole( c30, -6 ), " strange unique prime triplets up to 30", newline ) );
print( ( "Found ", whole( s count, -6 ), " strange unique prime triplets up to 1000", newline ) )
END
Output:
  1:   3 +   5 +  11 =  19
  2:   3 +   5 +  23 =  31
  3:   3 +   5 +  29 =  37
  4:   3 +   7 +  13 =  23
  5:   3 +   7 +  19 =  29
  6:   3 +  11 +  17 =  31
  7:   3 +  11 +  23 =  37
  8:   3 +  11 +  29 =  43
  9:   3 +  17 +  23 =  43
 10:   5 +   7 +  11 =  23
 11:   5 +   7 +  17 =  29
 12:   5 +   7 +  19 =  31
 13:   5 +   7 +  29 =  41
 14:   5 +  11 +  13 =  29
 15:   5 +  13 +  19 =  37
 16:   5 +  13 +  23 =  41
 17:   5 +  13 +  29 =  47
 18:   5 +  17 +  19 =  41
 19:   5 +  19 +  23 =  47
 20:   5 +  19 +  29 =  53
 21:   7 +  11 +  13 =  31
 22:   7 +  11 +  19 =  37
 23:   7 +  11 +  23 =  41
 24:   7 +  11 +  29 =  47
 25:   7 +  13 +  17 =  37
 26:   7 +  13 +  23 =  43
 27:   7 +  17 +  19 =  43
 28:   7 +  17 +  23 =  47
 29:   7 +  17 +  29 =  53
 30:   7 +  23 +  29 =  59
 31:  11 +  13 +  17 =  41
 32:  11 +  13 +  19 =  43
 33:  11 +  13 +  23 =  47
 34:  11 +  13 +  29 =  53
 35:  11 +  17 +  19 =  47
 36:  11 +  19 +  23 =  53
 37:  11 +  19 +  29 =  59
 38:  13 +  17 +  23 =  53
 39:  13 +  17 +  29 =  59
 40:  13 +  19 +  29 =  61
 41:  17 +  19 +  23 =  59
 42:  19 +  23 +  29 =  71
Found     42 strange unique prime triplets up to   30
Found 241580 strange unique prime triplets up to 1000

ALGOL W[edit]

Based on
Translation of: Wren
begin % find some strange unique primes - triplets of primes n, m, p %
 % where n + m + p is also prime and n =/= m =/= p  %
 % sets p( 1 :: n ) to a sieve of primes up to n %
procedure Eratosthenes ( logical array p( * ) ; integer value n ) ;
begin
p( 1 ) := false; p( 2 ) := true;
for i := 3 step 2 until n do p( i ) := true;
for i := 4 step 2 until n do p( i ) := false;
for i := 3 step 2 until truncate( sqrt( n ) ) do begin
integer ii; ii := i + i;
if p( i ) then for pr := i * i step ii until n do p( pr ) := false
end for_i ;
end Eratosthenes ;
 % we need to find the strange unique prime triplets below 1000 %
integer MAX_PRIME;
MAX_PRIME := 1000;
begin
 % the sum of the triplets could be (roughly) 3 x the largest prime %
logical array p ( 1 :: MAX_PRIME * 3 );
integer sCount, c30;
 % construct a sieve of primes up to MAX_PRIME * 3  %
Eratosthenes( p, MAX_PRIME * 3 );
 % count the strange prime triplets whose members are < 1000 and  %
 % whose sum is prime  %
sCount := c30 := 0;
 % 2 cannot be one of the primes as the sum would be even otherwise %
for n := 3 step 2 until MAX_PRIME - 5 do begin
if p( n ) then begin
for m := n + 2 step 2 until MAX_PRIME - 3 do begin
if p( m ) then begin
for l := m + 2 step 2 until MAX_PRIME do begin
if p( l ) then begin
integer s;
s := n + m + l;
if p( s ) then begin
sCount := sCount + 1;
if l <= 30 and m <= 30 and n <= 30 then begin
c30 := c30 + 1;
write( i_w := 3, s_w := 0, c30, ": ", n, " + ", m, " + ", l, " = ", s )
end if_l_m_n_le_30
end if_p_s
end if_p_l
end for_l
end if_p_m
end for_m
end if_p_n
end for_n ;
write( i_w := 3, s_w := 0, "Found ", c30, " strange unique prime triplets up to 30" );
write( i_w := 3, s_w := 0, "Found ", sCount, " strange unique prime triplets up to 1000" );
end
end.
Output:
  1:   3 +   5 +  11 =  19
  2:   3 +   5 +  23 =  31
  3:   3 +   5 +  29 =  37
  4:   3 +   7 +  13 =  23
  5:   3 +   7 +  19 =  29
  6:   3 +  11 +  17 =  31
  7:   3 +  11 +  23 =  37
  8:   3 +  11 +  29 =  43
  9:   3 +  17 +  23 =  43
 10:   5 +   7 +  11 =  23
 11:   5 +   7 +  17 =  29
 12:   5 +   7 +  19 =  31
 13:   5 +   7 +  29 =  41
 14:   5 +  11 +  13 =  29
 15:   5 +  13 +  19 =  37
 16:   5 +  13 +  23 =  41
 17:   5 +  13 +  29 =  47
 18:   5 +  17 +  19 =  41
 19:   5 +  19 +  23 =  47
 20:   5 +  19 +  29 =  53
 21:   7 +  11 +  13 =  31
 22:   7 +  11 +  19 =  37
 23:   7 +  11 +  23 =  41
 24:   7 +  11 +  29 =  47
 25:   7 +  13 +  17 =  37
 26:   7 +  13 +  23 =  43
 27:   7 +  17 +  19 =  43
 28:   7 +  17 +  23 =  47
 29:   7 +  17 +  29 =  53
 30:   7 +  23 +  29 =  59
 31:  11 +  13 +  17 =  41
 32:  11 +  13 +  19 =  43
 33:  11 +  13 +  23 =  47
 34:  11 +  13 +  29 =  53
 35:  11 +  17 +  19 =  47
 36:  11 +  19 +  23 =  53
 37:  11 +  19 +  29 =  59
 38:  13 +  17 +  23 =  53
 39:  13 +  17 +  29 =  59
 40:  13 +  19 +  29 =  61
 41:  17 +  19 +  23 =  59
 42:  19 +  23 +  29 =  71
Found  42 strange unique prime triplets up to   30
Found 241580 strange unique prime triplets up to 1000

AWK[edit]

 
# syntax: GAWK -f STRANGE_UNIQUE_PRIME_TRIPLETS.AWK
# converted from Go
BEGIN {
main(29,1)
main(999,0)
exit(0)
}
function main(n,show, count,i,j,k,s) {
for (i=3; i<=n-4; i+=2) {
if (is_prime(i)) {
for (j=i+2; j<=n-2; j+=2) {
if (is_prime(j)) {
for (k=j+2; k<=n; k+=2) {
if (is_prime(k)) {
s = i + j + k
if (is_prime(s)) {
count++
if (show == 1) {
printf("%2d + %2d + %2d = %d\n",i,j,k,s)
}
}
}
}
}
}
}
}
printf("Unique prime triples 2-%d which sum to a prime: %'d\n\n",n,count)
}
function is_prime(x, i) {
if (x <= 1) {
return(0)
}
for (i=2; i<=int(sqrt(x)); i++) {
if (x % i == 0) {
return(0)
}
}
return(1)
}
 
Output:
 3 +  5 + 11 = 19
 3 +  5 + 23 = 31
 3 +  5 + 29 = 37
 3 +  7 + 13 = 23
 3 +  7 + 19 = 29
 3 + 11 + 17 = 31
 3 + 11 + 23 = 37
 3 + 11 + 29 = 43
 3 + 17 + 23 = 43
 5 +  7 + 11 = 23
 5 +  7 + 17 = 29
 5 +  7 + 19 = 31
 5 +  7 + 29 = 41
 5 + 11 + 13 = 29
 5 + 13 + 19 = 37
 5 + 13 + 23 = 41
 5 + 13 + 29 = 47
 5 + 17 + 19 = 41
 5 + 19 + 23 = 47
 5 + 19 + 29 = 53
 7 + 11 + 13 = 31
 7 + 11 + 19 = 37
 7 + 11 + 23 = 41
 7 + 11 + 29 = 47
 7 + 13 + 17 = 37
 7 + 13 + 23 = 43
 7 + 17 + 19 = 43
 7 + 17 + 23 = 47
 7 + 17 + 29 = 53
 7 + 23 + 29 = 59
11 + 13 + 17 = 41
11 + 13 + 19 = 43
11 + 13 + 23 = 47
11 + 13 + 29 = 53
11 + 17 + 19 = 47
11 + 19 + 23 = 53
11 + 19 + 29 = 59
13 + 17 + 23 = 53
13 + 17 + 29 = 59
13 + 19 + 29 = 61
17 + 19 + 23 = 59
19 + 23 + 29 = 71
Unique prime triples 2-29 which sum to a prime: 42

Unique prime triples 2-999 which sum to a prime: 241,580

C[edit]

#include <stdbool.h>
#include <stdio.h>
#include <string.h>
 
#define LIMIT 3000
 
void init_sieve(unsigned char sieve[], int limit) {
int i, j;
 
for (i = 0; i < limit; i++) {
sieve[i] = 1;
}
sieve[0] = 0;
sieve[1] = 0;
 
for (i = 2; i < limit; i++) {
if (sieve[i]) {
for (j = i + i; j < limit; j += i) {
sieve[j] = 0;
}
}
}
}
 
void strange_unique_prime_triplets(unsigned char sieve[], int limit, bool verbose) {
int count = 0, sum;
int i, j, k, n, p;
int pi, pj, pk;
 
n = 0;
for (i = 0; i < limit; i++) {
if (sieve[i]) {
n++;
}
}
 
if (verbose) {
printf("Strange unique prime triplets < %d:\n", limit);
}
 
for (i = 0; i + 2 < n; i++) {
pi = 2;
p = i;
while (p > 0) {
pi++;
if (sieve[pi]) {
p--;
}
}
 
for (j = i + 1; j + 1 < n; j++) {
pj = pi;
p = j - i;
while (p > 0) {
pj++;
if (sieve[pj]) {
p--;
}
}
 
for (k = j + 1; k < n; k++) {
pk = pj;
p = k - j;
while (p > 0) {
pk++;
if (sieve[pk]) {
p--;
}
}
 
sum = pi + pj + pk;
if (sum < LIMIT && sieve[sum]) {
count++;
if (verbose) {
printf("%2d + %2d + %2d = %d\n", pi, pj, pk, sum);
}
}
}
}
}
 
printf("Count of strange unique prime triplets < %d is %d.\n\n", limit, count);
}
 
int main() {
unsigned char sieve[LIMIT];
 
init_sieve(sieve, LIMIT);
 
strange_unique_prime_triplets(sieve, 30, true);
strange_unique_prime_triplets(sieve, 1000, false);
 
return 0;
}
Output:
Strange unique prime triplets < 30:
 3 +  5 + 11 = 19
 3 +  5 + 23 = 31
 3 +  5 + 29 = 37
 3 +  7 + 13 = 23
 3 +  7 + 19 = 29
 3 + 11 + 17 = 31
 3 + 11 + 23 = 37
 3 + 11 + 29 = 43
 3 + 17 + 23 = 43
 5 +  7 + 11 = 23
 5 +  7 + 17 = 29
 5 +  7 + 19 = 31
 5 +  7 + 29 = 41
 5 + 11 + 13 = 29
 5 + 13 + 19 = 37
 5 + 13 + 23 = 41
 5 + 13 + 29 = 47
 5 + 17 + 19 = 41
 5 + 19 + 23 = 47
 5 + 19 + 29 = 53
 7 + 11 + 13 = 31
 7 + 11 + 19 = 37
 7 + 11 + 23 = 41
 7 + 11 + 29 = 47
 7 + 13 + 17 = 37
 7 + 13 + 23 = 43
 7 + 17 + 19 = 43
 7 + 17 + 23 = 47
 7 + 17 + 29 = 53
 7 + 23 + 29 = 59
11 + 13 + 17 = 41
11 + 13 + 19 = 43
11 + 13 + 23 = 47
11 + 13 + 29 = 53
11 + 17 + 19 = 47
11 + 19 + 23 = 53
11 + 19 + 29 = 59
13 + 17 + 23 = 53
13 + 17 + 29 = 59
13 + 19 + 29 = 61
17 + 19 + 23 = 59
19 + 23 + 29 = 71
Count of strange unique prime triplets < 30 is 42.

Count of strange unique prime triplets < 1000 is 241580.

C#[edit]

Just for fun, <30 sorted by sum, instead of order generated. One might think one should include the sieve generation time, but it is orders of magnitude smaller than the permute/sum time for these relatively low numbers.

using System; using System.Collections.Generic; using static System.Console; using System.Linq; using DT = System.DateTime;
 
class Program { static void Main(string[] args) { string s;
foreach (int lmt in new int[]{ 90, 300, 3000, 30000, 111000 }) {
var pr = PG.Primes(lmt).Skip(1).ToList(); DT st = DT.Now;
int d, f = 0; var r = new List<string>();
int i = -1, m, h = (m = lmt / 3), j, k, pra, prab;
while (i < 0) i = pr.IndexOf(h--); k = (j = i - 1) - 1;
for (int a = 0; a <= k; a++) { pra = pr[a];
for (int b = a + 1; b <= j; b++) { prab = pra + pr[b];
for (int c = b + 1; c <= i; c++) {
if (PG.flags[d = prab + pr[c]]) continue; f++;
if (lmt < 100) r.Add(string.Format("{3,5} = {0,2} + {1,2} + {2,2}", pra, pr[b], pr[c], d)); } } }
s = "s.u.p.t.s under "; r.Sort(); if (r.Count > 0) WriteLine("{0}{1}:\n{2}", s, m, string.Join("\n", r));
if (lmt > 100) WriteLine("Count of {0}{1,6:n0}: {2,13:n0} {3} sec", s, m, f, (DT.Now - st).ToString().Substring(6)); } } }
 
class PG { public static bool[] flags;
public static IEnumerable<int> Primes(int lim) {
flags = new bool[lim + 1]; int j = 2;
for (int d = 3, sq = 4; sq <= lim; j++, sq += d += 2)
if (!flags[j]) { yield return j;
for (int k = sq; k <= lim; k += j) flags[k] = true; }
for (; j <= lim; j++) if (!flags[j]) yield return j; } }
Output:

Timings from tio.run

s.u.p.t.s under 30:
   19 =  3 +  5 + 11
   23 =  3 +  7 + 13
   23 =  5 +  7 + 11
   29 =  3 +  7 + 19
   29 =  5 +  7 + 17
   29 =  5 + 11 + 13
   31 =  3 +  5 + 23
   31 =  3 + 11 + 17
   31 =  5 +  7 + 19
   31 =  7 + 11 + 13
   37 =  3 +  5 + 29
   37 =  3 + 11 + 23
   37 =  5 + 13 + 19
   37 =  7 + 11 + 19
   37 =  7 + 13 + 17
   41 =  5 +  7 + 29
   41 =  5 + 13 + 23
   41 =  5 + 17 + 19
   41 =  7 + 11 + 23
   41 = 11 + 13 + 17
   43 =  3 + 11 + 29
   43 =  3 + 17 + 23
   43 =  7 + 13 + 23
   43 =  7 + 17 + 19
   43 = 11 + 13 + 19
   47 =  5 + 13 + 29
   47 =  5 + 19 + 23
   47 =  7 + 11 + 29
   47 =  7 + 17 + 23
   47 = 11 + 13 + 23
   47 = 11 + 17 + 19
   53 =  5 + 19 + 29
   53 =  7 + 17 + 29
   53 = 11 + 13 + 29
   53 = 11 + 19 + 23
   53 = 13 + 17 + 23
   59 =  7 + 23 + 29
   59 = 11 + 19 + 29
   59 = 13 + 17 + 29
   59 = 17 + 19 + 23
   61 = 13 + 19 + 29
   71 = 19 + 23 + 29
Count of s.u.p.t.s under    100:           891  00.0000243 sec
Count of s.u.p.t.s under  1,000:       241,580  00.0054753 sec
Count of s.u.p.t.s under 10,000:    74,588,542  01.8159964 sec
Count of s.u.p.t.s under 37,000: 2,141,379,201  55.0369689 sec

C++[edit]

#include <iomanip>
#include <iostream>
#include <vector>
 
std::vector<bool> prime_sieve(size_t limit) {
std::vector<bool> sieve(limit, true);
if (limit > 0)
sieve[0] = false;
if (limit > 1)
sieve[1] = false;
for (size_t i = 4; i < limit; i += 2)
sieve[i] = false;
for (size_t p = 3; ; p += 2) {
size_t q = p * p;
if (q >= limit)
break;
if (sieve[p]) {
size_t inc = 2 * p;
for (; q < limit; q += inc)
sieve[q] = false;
}
}
return sieve;
}
 
void strange_unique_prime_triplets(int limit, bool verbose) {
std::vector<bool> sieve = prime_sieve(limit * 3);
std::vector<int> primes;
for (int p = 3; p < limit; p += 2) {
if (sieve[p])
primes.push_back(p);
}
size_t n = primes.size();
size_t count = 0;
if (verbose)
std::cout << "Strange unique prime triplets < " << limit << ":\n";
for (size_t i = 0; i + 2 < n; ++i) {
for (size_t j = i + 1; j + 1 < n; ++j) {
for (size_t k = j + 1; k < n; ++k) {
int sum = primes[i] + primes[j] + primes[k];
if (sieve[sum]) {
++count;
if (verbose) {
std::cout << std::setw(2) << primes[i] << " + "
<< std::setw(2) << primes[j] << " + "
<< std::setw(2) << primes[k] << " = " << sum
<< '\n';
}
}
}
}
}
std::cout << "\nCount of strange unique prime triplets < " << limit
<< " is " << count << ".\n";
}
 
int main() {
strange_unique_prime_triplets(30, true);
strange_unique_prime_triplets(1000, false);
return 0;
}
Output:
Strange unique prime triplets < 30:
 3 +  5 + 11 = 19
 3 +  5 + 23 = 31
 3 +  5 + 29 = 37
 3 +  7 + 13 = 23
 3 +  7 + 19 = 29
 3 + 11 + 17 = 31
 3 + 11 + 23 = 37
 3 + 11 + 29 = 43
 3 + 17 + 23 = 43
 5 +  7 + 11 = 23
 5 +  7 + 17 = 29
 5 +  7 + 19 = 31
 5 +  7 + 29 = 41
 5 + 11 + 13 = 29
 5 + 13 + 19 = 37
 5 + 13 + 23 = 41
 5 + 13 + 29 = 47
 5 + 17 + 19 = 41
 5 + 19 + 23 = 47
 5 + 19 + 29 = 53
 7 + 11 + 13 = 31
 7 + 11 + 19 = 37
 7 + 11 + 23 = 41
 7 + 11 + 29 = 47
 7 + 13 + 17 = 37
 7 + 13 + 23 = 43
 7 + 17 + 19 = 43
 7 + 17 + 23 = 47
 7 + 17 + 29 = 53
 7 + 23 + 29 = 59
11 + 13 + 17 = 41
11 + 13 + 19 = 43
11 + 13 + 23 = 47
11 + 13 + 29 = 53
11 + 17 + 19 = 47
11 + 19 + 23 = 53
11 + 19 + 29 = 59
13 + 17 + 23 = 53
13 + 17 + 29 = 59
13 + 19 + 29 = 61
17 + 19 + 23 = 59
19 + 23 + 29 = 71

Count of strange unique prime triplets < 30 is 42.

Count of strange unique prime triplets < 1000 is 241580.

Delphi[edit]

Translation of: Go
 
program Strange_primes;
 
{$APPTYPE CONSOLE}
 
uses
System.SysUtils;
 
function IsPrime(n: Integer): Boolean;
begin
if n < 2 then
exit(false);
 
if n mod 2 = 0 then
exit(n = 2);
 
if n mod 3 = 0 then
exit(n = 3);
 
var d := 5;
while d * d <= n do
begin
if n mod d = 0 then
exit(false);
 
inc(d, 2);
 
if n mod d = 0 then
exit(false);
 
inc(d, 4);
end;
Result := true;
end;
 
function Commatize(value: Integer): string;
begin
Result := FloatToStrF(value, ffNumber, 10, 0);
end;
 
function StrangePrimes(n: Integer; countOnly: Boolean): Integer;
begin
var c := 0;
var f := '%2d: %2d + %2d + %2d = %2d'#10;
var s: Integer := 0;
 
var i := 3;
while i <= n - 4 do
begin
if IsPrime(i) then
begin
var j := i + 2;
while j <= n - 2 do
begin
if IsPrime(j) then
begin
var k := j + 2;
while k <= n do
begin
if IsPrime(k) then
begin
s := i + j + k;
if IsPrime(s) then
begin
inc(c);
if not countOnly then
write(format(f, [c, i, j, k, s]));
end;
end;
inc(k, 2);
end;
end;
inc(j, 2);
end;
end;
inc(i, 2);
end;
Result := c;
end;
 
begin
Writeln('Unique prime triples under 30 which sum to a prime:');
strangePrimes(29, false);
var cs := commatize(strangePrimes(999, true));
writeln('There are ', cs, ' unique prime triples under 1,000 which sum to a prime.');
readln;
end.

F#[edit]

This task uses Extensible Prime Generator (F#).

 
// Strange unique prime triplets. Nigel Galloway: March 12th., 2021
let sP n=let N=primes32()|>Seq.takeWhile((>)n)|>Array.ofSeq
seq{for n in 0..N.Length-1 do for i in n+1..N.Length-1 do for g in i+1..N.Length-1->(N.[n],N.[i],N.[g])}|>Seq.filter(fun(n,i,g)->isPrime(n+i+g))
sP 30|>Seq.iteri(fun n(i,g,l)->printfn "%2d: %2d+%2d+%2d=%2d")
printfn "%d" (Seq.length(sP 1000))
printfn "%d" (Seq.length(sP 10000))
 
Output:
241580
74588542

Factor[edit]

USING: formatting io kernel math math.combinatorics math.primes
sequences tools.memory.private ;
 
: .triplet ( seq -- ) "%2d+%2d+%2d = %d\n" vprintf ;
 
: strange ( n -- )
primes-upto 3
[ dup sum dup prime? [ suffix .triplet ] [ 2drop ] if ]
each-combination ;
 
: count-strange ( n -- count )
0 swap primes-upto 3
[ sum prime? [ 1 + ] when ] each-combination ;
 
30 strange
1,000 count-strange commas nl
"Found %s strange prime triplets with n, m, p < 1,000.\n" printf
Output:
 3+ 5+11 = 19
 3+ 5+23 = 31
 3+ 5+29 = 37
 3+ 7+13 = 23
 3+ 7+19 = 29
 3+11+17 = 31
 3+11+23 = 37
 3+11+29 = 43
 3+17+23 = 43
 5+ 7+11 = 23
 5+ 7+17 = 29
 5+ 7+19 = 31
 5+ 7+29 = 41
 5+11+13 = 29
 5+13+19 = 37
 5+13+23 = 41
 5+13+29 = 47
 5+17+19 = 41
 5+19+23 = 47
 5+19+29 = 53
 7+11+13 = 31
 7+11+19 = 37
 7+11+23 = 41
 7+11+29 = 47
 7+13+17 = 37
 7+13+23 = 43
 7+17+19 = 43
 7+17+23 = 47
 7+17+29 = 53
 7+23+29 = 59
11+13+17 = 41
11+13+19 = 43
11+13+23 = 47
11+13+29 = 53
11+17+19 = 47
11+19+23 = 53
11+19+29 = 59
13+17+23 = 53
13+17+29 = 59
13+19+29 = 61
17+19+23 = 59
19+23+29 = 71

Found 241,580 strange prime triplets with n, m, p < 1,000.

Fermat[edit]

Function IsSUPT(n,m,p) = 
if Isprime(n) and Isprime(m) and Isprime(p) and Isprime(n+m+p) then 1 else 0 fi.
 
for n=3 to 19 do
for m=n+2 to 23 do
for p=m+2 to 29 do
if IsSUPT(n,m,p) then !!(n,m,p) fi;
od;
od;
od

I'll leave the stretch goal for someone else.

FreeBASIC[edit]

Use the function at Primality by trial division#FreeBASIC as an include; I can't be bothered reproducing it here.

#include"isprime.bas"
 
dim as uinteger c = 0
 
for p as uinteger = 3 to 997
if not isprime(p) then continue for
for m as uinteger = p + 1 to 998
if not isprime(m) then continue for
for n as uinteger = m + 1 to 999
if not isprime(n) then continue for
if isprime(p + n + m) then
c = c + 1
if n < 30 then print p;" + ";m;" + ";n;" = "; p + m + n
end if
next n
next m
next p
 
print "There are ";c;" triples below 1000."
Output:
3 + 5 + 11 = 19

3 + 5 + 23 = 31 3 + 5 + 29 = 37 3 + 7 + 13 = 23 3 + 7 + 19 = 29 3 + 11 + 17 = 31 3 + 11 + 23 = 37 3 + 11 + 29 = 43 3 + 17 + 23 = 43 5 + 7 + 11 = 23 5 + 7 + 17 = 29 5 + 7 + 19 = 31 5 + 7 + 29 = 41 5 + 11 + 13 = 29 5 + 13 + 19 = 37 5 + 13 + 23 = 41 5 + 13 + 29 = 47 5 + 17 + 19 = 41 5 + 19 + 23 = 47 5 + 19 + 29 = 53 7 + 11 + 13 = 31 7 + 11 + 19 = 37 7 + 11 + 23 = 41 7 + 11 + 29 = 47 7 + 13 + 17 = 37 7 + 13 + 23 = 43 7 + 17 + 19 = 43 7 + 17 + 23 = 47 7 + 17 + 29 = 53 7 + 23 + 29 = 59 11 + 13 + 17 = 41 11 + 13 + 19 = 43 11 + 13 + 23 = 47 11 + 13 + 29 = 53 11 + 17 + 19 = 47 11 + 19 + 23 = 53 11 + 19 + 29 = 59 13 + 17 + 23 = 53 13 + 17 + 29 = 59 13 + 19 + 29 = 61 17 + 19 + 23 = 59 19 + 23 + 29 = 71

There are 241580 triples below 1000.

Forth[edit]

Works with: Gforth
: prime? ( n -- ? ) here + [email protected] 0= ;
: notprime! ( n -- ) here + 1 swap c! ;
 
: prime_sieve ( n -- )
here over erase
0 notprime!
1 notprime!
dup 4 > if
dup 4 do i notprime! 2 +loop
then
3
begin
2dup dup * >
while
dup prime? if
2dup dup * do
i notprime!
dup 2* +loop
then
2 +
repeat
2drop ;
 
: print_strange_unique_prime_triplets ( n -- )
dup 8 < if drop exit then
dup 3 * prime_sieve
dup 4 - 3 do
i prime? if
dup 2 - i 2 + do
i prime? if
dup i 2 + do
i prime? if
i j k + + dup prime? if
k 2 .r ." + " j 2 .r ." + " i 2 .r ." = " 2 .r cr
else
drop
then
then
2 +loop
then
2 +loop
then
2 +loop drop ;
 
: count_strange_unique_prime_triplets ( n -- n )
dup 8 < if drop 0 exit then
dup 3 * prime_sieve
0 swap
dup 4 - 3 do
i prime? if
dup 2 - i 2 + do
i prime? if
dup i 2 + do
i prime? if
i j k + + prime? if
swap 1+ swap
then
then
2 +loop
then
2 +loop
then
2 +loop drop ;
 
." Strange unique prime triplets < 30:" cr
30 print_strange_unique_prime_triplets
 
." Count of strange unique prime triplets < 1000: "
1000 count_strange_unique_prime_triplets . cr
bye
Output:
Strange unique prime triplets < 30:
 3 +  5 + 11 = 19
 3 +  5 + 23 = 31
 3 +  5 + 29 = 37
 3 +  7 + 13 = 23
 3 +  7 + 19 = 29
 3 + 11 + 17 = 31
 3 + 11 + 23 = 37
 3 + 11 + 29 = 43
 3 + 17 + 23 = 43
 5 +  7 + 11 = 23
 5 +  7 + 17 = 29
 5 +  7 + 19 = 31
 5 +  7 + 29 = 41
 5 + 11 + 13 = 29
 5 + 13 + 19 = 37
 5 + 13 + 23 = 41
 5 + 13 + 29 = 47
 5 + 17 + 19 = 41
 5 + 19 + 23 = 47
 5 + 19 + 29 = 53
 7 + 11 + 13 = 31
 7 + 11 + 19 = 37
 7 + 11 + 23 = 41
 7 + 11 + 29 = 47
 7 + 13 + 17 = 37
 7 + 13 + 23 = 43
 7 + 17 + 19 = 43
 7 + 17 + 23 = 47
 7 + 17 + 29 = 53
 7 + 23 + 29 = 59
11 + 13 + 17 = 41
11 + 13 + 19 = 43
11 + 13 + 23 = 47
11 + 13 + 29 = 53
11 + 17 + 19 = 47
11 + 19 + 23 = 53
11 + 19 + 29 = 59
13 + 17 + 23 = 53
13 + 17 + 29 = 59
13 + 19 + 29 = 61
17 + 19 + 23 = 59
19 + 23 + 29 = 71
Count of strange unique prime triplets < 1000: 241580 

Fōrmulæ[edit]

Fōrmulæ programs are not textual, visualization/edition of programs is done showing/manipulating structures but not text. Moreover, there can be multiple visual representations of the same program. Even though it is possible to have textual representation —i.e. XML, JSON— they are intended for storage and transfer purposes more than visualization and edition.

Programs in Fōrmulæ are created/edited online in its website, However they run on execution servers. By default remote servers are used, but they are limited in memory and processing power, since they are intended for demonstration and casual use. A local server can be downloaded and installed, it has no limitations (it runs in your own computer). Because of that, example programs can be fully visualized and edited, but some of them will not run if they require a moderate or heavy computation/memory resources, and no local server is being used.

In this page you can see the program(s) related to this task and their results.

Go[edit]

Basic[edit]

Translation of: Wren
package main
 
import "fmt"
 
func isPrime(n int) bool {
switch {
case n < 2:
return false
case n%2 == 0:
return n == 2
case n%3 == 0:
return n == 3
default:
d := 5
for d*d <= n {
if n%d == 0 {
return false
}
d += 2
if n%d == 0 {
return false
}
d += 4
}
return true
}
}
 
func commatize(n int) string {
s := fmt.Sprintf("%d", n)
if n < 0 {
s = s[1:]
}
le := len(s)
for i := le - 3; i >= 1; i -= 3 {
s = s[0:i] + "," + s[i:]
}
if n >= 0 {
return s
}
return "-" + s
}
 
func strangePrimes(n int, countOnly bool) int {
c := 0
f := "%2d: %2d + %2d + %2d = %2d\n"
var s int
 
for i := 3; i <= n-4; i += 2 {
if isPrime(i) {
for j := i + 2; j <= n-2; j += 2 {
if isPrime(j) {
for k := j + 2; k <= n; k += 2 {
if isPrime(k) {
s = i + j + k
if isPrime(s) {
c++
if !countOnly {
fmt.Printf(f, c, i, j, k, s)
}
}
}
}
}
}
}
}
return c
}
 
func main() {
fmt.Println("Unique prime triples under 30 which sum to a prime:")
strangePrimes(29, false)
cs := commatize(strangePrimes(999, true))
fmt.Printf("\nThere are %s unique prime triples under 1,000 which sum to a prime.\n", cs)
}
Output:
Unique prime triples under 30 which sum to a prime:
 1:  3 +  5 + 11 = 19
 2:  3 +  5 + 23 = 31
 3:  3 +  5 + 29 = 37
 4:  3 +  7 + 13 = 23
 5:  3 +  7 + 19 = 29
 6:  3 + 11 + 17 = 31
 7:  3 + 11 + 23 = 37
 8:  3 + 11 + 29 = 43
 9:  3 + 17 + 23 = 43
10:  5 +  7 + 11 = 23
11:  5 +  7 + 17 = 29
12:  5 +  7 + 19 = 31
13:  5 +  7 + 29 = 41
14:  5 + 11 + 13 = 29
15:  5 + 13 + 19 = 37
16:  5 + 13 + 23 = 41
17:  5 + 13 + 29 = 47
18:  5 + 17 + 19 = 41
19:  5 + 19 + 23 = 47
20:  5 + 19 + 29 = 53
21:  7 + 11 + 13 = 31
22:  7 + 11 + 19 = 37
23:  7 + 11 + 23 = 41
24:  7 + 11 + 29 = 47
25:  7 + 13 + 17 = 37
26:  7 + 13 + 23 = 43
27:  7 + 17 + 19 = 43
28:  7 + 17 + 23 = 47
29:  7 + 17 + 29 = 53
30:  7 + 23 + 29 = 59
31: 11 + 13 + 17 = 41
32: 11 + 13 + 19 = 43
33: 11 + 13 + 23 = 47
34: 11 + 13 + 29 = 53
35: 11 + 17 + 19 = 47
36: 11 + 19 + 23 = 53
37: 11 + 19 + 29 = 59
38: 13 + 17 + 23 = 53
39: 13 + 17 + 29 = 59
40: 13 + 19 + 29 = 61
41: 17 + 19 + 23 = 59
42: 19 + 23 + 29 = 71

There are 241,580 unique prime triples under 1,000 which sum to a prime.

Faster[edit]

Translation of: Wren
package main
 
import "fmt"
 
var sieved []bool
var p = []int{2}
 
func sieve(limit int) []bool {
limit++
// True denotes composite, false denotes prime.
c := make([]bool, limit) // all false by default
c[0] = true
c[1] = true
// no need to bother with even numbers over 2 for this task
p := 3 // Start from 3.
for {
p2 := p * p
if p2 >= limit {
break
}
for i := p2; i < limit; i += 2 * p {
c[i] = true
}
for {
p += 2
if !c[p] {
break
}
}
}
return c
}
 
func commatize(n int) string {
s := fmt.Sprintf("%d", n)
if n < 0 {
s = s[1:]
}
le := len(s)
for i := le - 3; i >= 1; i -= 3 {
s = s[0:i] + "," + s[i:]
}
if n >= 0 {
return s
}
return "-" + s
}
 
func strangePrimes(n int, countOnly bool) int {
c := 0
f := "%2d: %2d + %2d + %2d = %2d\n"
var r, s int
m := 0
for ; m < len(p) && p[m] <= n; m++ {
}
for i := 1; i < m-2; i++ {
for j := i + 1; j < m-1; j++ {
r = p[i] + p[j]
for k := j + 1; k < m; k++ {
s = r + p[k]
if !sieved[s] {
c++
if !countOnly {
fmt.Printf(f, c, p[i], p[j], p[k], s)
}
}
}
}
}
return c
}
 
func main() {
const max = 1000
sieved = sieve(3*max)
for i := 3; i <= max; i += 2 {
if !sieved[i] {
p = append(p, i)
}
}
fmt.Println("Unique prime triples under 30 which sum to a prime:")
strangePrimes(29, false)
cs := commatize(strangePrimes(999, true))
fmt.Printf("\nThere are %s unique prime triples under 1,000 which sum to a prime.\n", cs)
}
Output:

Same as 'basic' version.

Java[edit]

import java.util.*;
 
public class StrangeUniquePrimeTriplets {
public static void main(String[] args) {
strangeUniquePrimeTriplets(30, true);
strangeUniquePrimeTriplets(1000, false);
}
 
private static void strangeUniquePrimeTriplets(int limit, boolean verbose) {
boolean[] sieve = primeSieve(limit * 3);
List<Integer> primeList = new ArrayList<>();
for (int p = 3; p < limit; p += 2) {
if (sieve[p])
primeList.add(p);
}
int n = primeList.size();
// Convert object list to primitive array for performance
int[] primes = new int[n];
for (int i = 0; i < n; ++i)
primes[i] = primeList.get(i);
int count = 0;
if (verbose)
System.out.printf("Strange unique prime triplets < %d:\n", limit);
for (int i = 0; i + 2 < n; ++i) {
for (int j = i + 1; j + 1 < n; ++j) {
int s = primes[i] + primes[j];
for (int k = j + 1; k < n; ++k) {
int sum = s + primes[k];
if (sieve[sum]) {
++count;
if (verbose)
System.out.printf("%2d + %2d + %2d = %2d\n", primes[i], primes[j], primes[k], sum);
}
}
}
}
System.out.printf("\nCount of strange unique prime triplets < %d is %d.\n", limit, count);
}
 
private static boolean[] primeSieve(int limit) {
boolean[] sieve = new boolean[limit];
Arrays.fill(sieve, true);
if (limit > 0)
sieve[0] = false;
if (limit > 1)
sieve[1] = false;
for (int i = 4; i < limit; i += 2)
sieve[i] = false;
for (int p = 3; ; p += 2) {
int q = p * p;
if (q >= limit)
break;
if (sieve[p]) {
int inc = 2 * p;
for (; q < limit; q += inc)
sieve[q] = false;
}
}
return sieve;
}
}
Output:
Strange unique prime triplets < 30:
 3 +  5 + 11 = 19
 3 +  5 + 23 = 31
 3 +  5 + 29 = 37
 3 +  7 + 13 = 23
 3 +  7 + 19 = 29
 3 + 11 + 17 = 31
 3 + 11 + 23 = 37
 3 + 11 + 29 = 43
 3 + 17 + 23 = 43
 5 +  7 + 11 = 23
 5 +  7 + 17 = 29
 5 +  7 + 19 = 31
 5 +  7 + 29 = 41
 5 + 11 + 13 = 29
 5 + 13 + 19 = 37
 5 + 13 + 23 = 41
 5 + 13 + 29 = 47
 5 + 17 + 19 = 41
 5 + 19 + 23 = 47
 5 + 19 + 29 = 53
 7 + 11 + 13 = 31
 7 + 11 + 19 = 37
 7 + 11 + 23 = 41
 7 + 11 + 29 = 47
 7 + 13 + 17 = 37
 7 + 13 + 23 = 43
 7 + 17 + 19 = 43
 7 + 17 + 23 = 47
 7 + 17 + 29 = 53
 7 + 23 + 29 = 59
11 + 13 + 17 = 41
11 + 13 + 19 = 43
11 + 13 + 23 = 47
11 + 13 + 29 = 53
11 + 17 + 19 = 47
11 + 19 + 23 = 53
11 + 19 + 29 = 59
13 + 17 + 23 = 53
13 + 17 + 29 = 59
13 + 19 + 29 = 61
17 + 19 + 23 = 59
19 + 23 + 29 = 71

Count of strange unique prime triplets < 30 is 42.

Count of strange unique prime triplets < 1000 is 241580.

jq[edit]

Works with: jq

Works with gojq, the Go implementation of jq

See e.g. Erdős-primes#jq for a suitable implementation of `is_prime`.

def count(s): reduce s as $x (null; .+1);
 
def task($n):
[2, (range(3;$n;2)|select(is_prime))]
| . as $p
| range(0; length) as $i
| range($i+1; length) as $j
| range($j+1; length) as $k
| [.[$i], .[$j], .[$k]]
| select( add| is_prime) ;
 
task(30),
"\nStretch goal: \(count(task(1000)))"
Output:
[3,5,11]
[3,5,23]
[3,5,29]
[3,7,13]
[3,7,19]
[3,11,17]
[3,11,23]
[3,11,29]
[3,17,23]
[5,7,11]
[5,7,17]
[5,7,19]
[5,7,29]
[5,11,13]
[5,13,19]
[5,13,23]
[5,13,29]
[5,17,19]
[5,19,23]
[5,19,29]
[7,11,13]
[7,11,19]
[7,11,23]
[7,11,29]
[7,13,17]
[7,13,23]
[7,17,19]
[7,17,23]
[7,17,29]
[7,23,29]
[11,13,17]
[11,13,19]
[11,13,23]
[11,13,29]
[11,17,19]
[11,19,23]
[11,19,29]
[13,17,23]
[13,17,29]
[13,19,29]
[17,19,23]
[19,23,29]

Stretch goal: 241580

Julia[edit]

using Primes
 
function prime_sum_prime_triplets_to(N, verbose=false)
a = primes(3, N)
prime_sieve_set = primesmask(1, N * 3)
len, triplets, n = length(a), Dict{Tuple{Int64,Int64,Int64}, Int}(), 0
for i in eachindex(a), j in i+1:len, k in j+1:len
if prime_sieve_set[a[i] + a[j] + a[k]]
verbose && (triplets[(a[i], a[j], a[k])] = 1)
n += 1
end
end
if verbose
len = (length(string(N)) + 2) * 3
println("\n", rpad("Triplet", len), "Sum\n", "-"^(len+3))
for k in sort(collect(keys(triplets)), lt = (x, y) -> collect(x) < collect(y))
println(rpad(k, len), sum(k))
end
end
println("\n\n$n unique triplets of 3 primes between 2 and $N sum to a prime.")
return triplets
end
 
prime_sum_prime_triplets_to(30, true)
prime_sum_prime_triplets_to(1000)
@time prime_sum_prime_triplets_to(10000)
@time prime_sum_prime_triplets_to(100000)
 
Output:
Triplet     Sum
---------------
(3, 5, 11)  19
(3, 5, 23)  31
(3, 5, 29)  37
(3, 7, 13)  23
(3, 7, 19)  29
(3, 11, 17) 31
(3, 11, 23) 37
(3, 11, 29) 43
(3, 17, 23) 43
(5, 7, 11)  23
(5, 7, 17)  29
(5, 7, 19)  31
(5, 7, 29)  41
(5, 11, 13) 29
(5, 13, 19) 37
(5, 13, 23) 41
(5, 13, 29) 47
(5, 17, 19) 41
(5, 19, 23) 47
(5, 19, 29) 53
(7, 11, 13) 31
(7, 11, 19) 37
(7, 11, 23) 41
(7, 11, 29) 47
(7, 13, 17) 37
(7, 13, 23) 43
(7, 17, 19) 43
(7, 17, 23) 47
(7, 17, 29) 53
(7, 23, 29) 59
(11, 13, 17)41
(11, 13, 19)43
(11, 13, 23)47
(11, 13, 29)53
(11, 17, 19)47
(11, 19, 23)53
(11, 19, 29)59
(13, 17, 23)53
(13, 17, 29)59
(13, 19, 29)61
(17, 19, 23)59
(19, 23, 29)71


42 unique triplets of 3 primes between 2 and 30 sum to a prime.


241580 unique triplets of 3 primes between 2 and 1000 sum to a prime.


74588542 unique triplets of 3 primes between 2 and 10000 sum to a prime.
  0.509732 seconds (31 allocations: 25.938 KiB)


28694800655 unique triplets of 3 primes between 2 and 100000 sum to a prime.
224.940756 seconds (35 allocations: 218.156 KiB)

Mathematica/Wolfram Language[edit]

p = Prime[[email protected][30]];
Select[Subsets[p, {3}], Total/*PrimeQ]
 
p = Prime[[email protected][1000]];
Length[Select[Subsets[p, {3}], Total/*PrimeQ]]
Output:
{{3,5,11},{3,5,23},{3,5,29},{3,7,13},{3,7,19},{3,11,17},{3,11,23},{3,11,29},{3,17,23},{5,7,11},{5,7,17},{5,7,19},{5,7,29},{5,11,13},{5,13,19},{5,13,23},{5,13,29},{5,17,19},{5,19,23},{5,19,29},{7,11,13},{7,11,19},{7,11,23},{7,11,29},{7,13,17},{7,13,23},{7,17,19},{7,17,23},{7,17,29},{7,23,29},{11,13,17},{11,13,19},{11,13,23},{11,13,29},{11,17,19},{11,19,23},{11,19,29},{13,17,23},{13,17,29},{13,19,29},{17,19,23},{19,23,29}}
241580

Nim[edit]

import strformat, strutils, sugar
 
func isPrime(n: Positive): bool =
if n < 2: return false
if n mod 2 == 0: return n == 2
if n mod 3 == 0: return n == 3
var d = 5
while d * d <= n:
if n mod d == 0: return false
inc d, 2
if n mod d == 0: return false
inc d, 4
result = true
 
 
iterator triplets(primes: openArray[int]): (int, int, int) =
## Yield the triplets.
for i in 0..primes.high-2:
let n = primes[i]
for j in (i+1)..primes.high-1:
let m = primes[j]
for k in (j+1)..primes.high:
let p = primes[k]
if (n + m + p).isPrime:
yield (n, m, p)
 
 
const Primes30 = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
echo "List of strange unique prime triplets for n < m < p < 30:"
for (n, m, p) in Primes30.triplets():
echo &"{n:2} + {m:2} + {p:2} = {n+m+p}"
 
echo()
const Primes1000 = collect(newSeq):
for n in 2..999:
if n.isPrime: n
var count = 0
for _ in Primes1000.triplets(): inc count
echo "Count of strange unique prime triplets for n < m < p < 1000: ", ($count).insertSep()
Output:
List of strange unique prime triplets for n < m < p < 30:
 3 +  5 + 11 = 19
 3 +  5 + 23 = 31
 3 +  5 + 29 = 37
 3 +  7 + 13 = 23
 3 +  7 + 19 = 29
 3 + 11 + 17 = 31
 3 + 11 + 23 = 37
 3 + 11 + 29 = 43
 3 + 17 + 23 = 43
 5 +  7 + 11 = 23
 5 +  7 + 17 = 29
 5 +  7 + 19 = 31
 5 +  7 + 29 = 41
 5 + 11 + 13 = 29
 5 + 13 + 19 = 37
 5 + 13 + 23 = 41
 5 + 13 + 29 = 47
 5 + 17 + 19 = 41
 5 + 19 + 23 = 47
 5 + 19 + 29 = 53
 7 + 11 + 13 = 31
 7 + 11 + 19 = 37
 7 + 11 + 23 = 41
 7 + 11 + 29 = 47
 7 + 13 + 17 = 37
 7 + 13 + 23 = 43
 7 + 17 + 19 = 43
 7 + 17 + 23 = 47
 7 + 17 + 29 = 53
 7 + 23 + 29 = 59
11 + 13 + 17 = 41
11 + 13 + 19 = 43
11 + 13 + 23 = 47
11 + 13 + 29 = 53
11 + 17 + 19 = 47
11 + 19 + 23 = 53
11 + 19 + 29 = 59
13 + 17 + 23 = 53
13 + 17 + 29 = 59
13 + 19 + 29 = 61
17 + 19 + 23 = 59
19 + 23 + 29 = 71

Count of strange unique prime triplets for n < m < p < 1000: 241_580

Pascal[edit]

Works with: Free Pascal
program PrimeTriplets;
//Free Pascal Compiler version 3.2.1 [2020/11/03] for x86_64fpc 3.2.1
{$IFDEF FPC}
{$MODE DELPHI}
{$Optimization ON,ALL}
{$ELSE}
{$APPTYPE CONSOLE}
{$ENDIF}
const
MAXZAHL = 100000;// > 3
MAXSUM = 3*MAXZAHL;
 
CountOfPrimes = trunc(MAXZAHL/(ln(MAXZAHL)-1.08))+100;
 
type
tChkprimes = array[0..MAXSUM] of byte;//prime == 1 , nonprime == 0
var
Chkprimes:tChkprimes;
primes : array[0..CountOfPrimes]of Uint32;//here starting with 3
count,primeCount:NativeInt;
 
procedure InitPrimes;
//sieve of eratothenes
var
i,j : NativeInt;
begin
fillchar(Chkprimes,SizeOf(tChkprimes),#1);
i := 2;
j := 2*2;
if j> MAXSUM then
EXIT;
repeat
Chkprimes[j]:= 0;
inc(j,i);
until j> Maxsum;
 
For i := 3 to MAXSUM do
Begin
if Chkprimes[i] <>0 then
Begin
j := i*i;
if j> MAXSUM then
Break;
repeat
Chkprimes[j]:= 0;
inc(j,2*i);
until j> Maxsum;
end;
end;
 
j := 0;
For i := 3 to MAXZAHL do
IF Chkprimes[i]<>0 then
Begin
primes[j] := i;
inc(j);
end;
primeCount := j-1;
j :=CountOfPrimes -primeCount;
 
IF j <0 then
begin
writeln(' Need more space for primes ', -j);
HALT(-243);
end;
end;
 
function GetMaxPrimeIdx(lmt:NativeInt):NativeInt;
begin
if lmt >= Maxzahl then
Begin
result := primecount;
EXIT;
end;
 
result := 0;
while (result < primecount) AND (primes[result]<lmt) do
inc(result);
dec(result);
end;
 
procedure Out_Check(lmt:nativeInt);
//simplest version
var
i,j,k,s,pc: NativeInt;
Begin
pc:= GetMaxPrimeIdx(lmt);
count := 0;
For i := 0 to pc do
For j := i+1 to pc do
For k := j+1 to pc do
Begin
s := primes[i]+primes[j]+Primes[k];
//if takes the longest time
if ChkPrimes[s]<> 0 then
begin
inc(count);
writeln(count:3,': ',primes[i],'+',primes[j],'+',primes[k],' = ',s);
end;
end;
writeln;
end;
 
procedure Count_Check(pc:nativeInt);
// the power of many registers ( 64-Bit )
var
cnt : Uint64;
pPrimes : pUint32;
pChkPrimes : ^tChkprimes;
pi,pij,i,j,k: NativeInt;
Begin
cnt := 0;
pPrimes := @primes[0];
pChkPrimes := @Chkprimes[0];
For i := 0 to pc do
Begin
pi := pPrimes[i];
For j := i+1 to pc do
begin
pij := pi+pPrimes[j];
For k := j+1 to pc do
inc(cnt,pChkPrimes^[pij+pPrimes[k]]);
end;
end;
count := cnt;
end;
 
procedure Check_Limit(lmt:NativeInt);
Begin
If lmt>primes[primecount] then
lmt := MaxZahl;
write('Limit = ',lmt,' count: ');
Count_Check(GetMaxPrimeIdx(lmt));
writeln(count);
end;
 
BEGIN
InitPrimes;
Out_Check(30);
Check_Limit(100);
Check_Limit(1000);
Check_Limit(10000);
//Check_Limit(MAXZAHL);
END.
Output:
  1: 3+5+11 = 19
  2: 3+5+23 = 31
  3: 3+5+29 = 37
  4: 3+7+13 = 23
  5: 3+7+19 = 29
  6: 3+11+17 = 31
  7: 3+11+23 = 37
  8: 3+11+29 = 43
  9: 3+17+23 = 43
 10: 5+7+11 = 23
 11: 5+7+17 = 29
 12: 5+7+19 = 31
 13: 5+7+29 = 41
 14: 5+11+13 = 29
 15: 5+13+19 = 37
 16: 5+13+23 = 41
 17: 5+13+29 = 47
 18: 5+17+19 = 41
 19: 5+19+23 = 47
 20: 5+19+29 = 53
 21: 7+11+13 = 31
 22: 7+11+19 = 37
 23: 7+11+23 = 41
 24: 7+11+29 = 47
 25: 7+13+17 = 37
 26: 7+13+23 = 43
 27: 7+17+19 = 43
 28: 7+17+23 = 47
 29: 7+17+29 = 53
 30: 7+23+29 = 59
 31: 11+13+17 = 41
 32: 11+13+19 = 43
 33: 11+13+23 = 47
 34: 11+13+29 = 53
 35: 11+17+19 = 47
 36: 11+19+23 = 53
 37: 11+19+29 = 59
 38: 13+17+23 = 53
 39: 13+17+29 = 59
 40: 13+19+29 = 61
 41: 17+19+23 = 59
 42: 19+23+29 = 71

Limit = 100 count: 891
Limit = 1000 count: 241580
Limit = 10000 count: 74588542
//real    0m0,142s
Limit = 100000 count: 28694800655
real    1m5,378s

Perl[edit]

Library: ntheory
use strict;
use warnings;
use List::Util 'sum';
use ntheory <primes is_prime>;
use Algorithm::Combinatorics 'combinations';
 
for my $n (30, 1000) {
printf "Found %d strange unique prime triplets up to $n.\n",
scalar grep { is_prime(sum @$_) } combinations(primes($n), 3);
}
Output:
Found 42 strange unique prime triplets up to 30.
Found 241580 strange unique prime triplets up to 1000.

Phix[edit]

with javascript_semantics
requires("0.8.4")
function create_sieve(integer limit)
    sequence sieve = repeat(true,limit)
    sieve[1] = false
    for i=4 to limit by 2 do
        sieve[i] = false
    end for
    for p=3 to floor(sqrt(limit)) by 2 do
        integer p2 = p*p
        if sieve[p2] then
            for k=p2 to limit by p*2 do
                sieve[k] = false
            end for
        end if
    end for
    return sieve
end function
 
procedure strange_triplets(integer lim, bool bCountOnly=true)
    atom t0 = time(), t1 = t0+1
    sequence primes = get_primes_le(lim),
             sieve = create_sieve(lim*3),
             res = {}
    atom count = 0
    --
    -- It is not worth involving 2, ie primes[1],
    -- since (2 + any other two primes) is even,
    -- also we may as well leave space for {j,k},
    -- {k} in the two outer loops.
    -- Using a sieve on the inner test is over
    -- ten times faster than is_prime(), whereas
    -- using a separate table of primes for the
    -- two outer loops is about twice as fast as 
    -- scanning the sieve skipping falsies. Also
    -- interestingly, using nm = n+m is twice as
    -- fast as nmp = n+m+p.
    --
    for i=2 to length(primes)-2 do
        integer n = primes[i]
        for j=i+1 to length(primes)-1 do
            integer m = primes[j],
                    nm = n+m
            for k=j+1 to length(primes) do
                integer p = primes[k],
                        nmp = nm+p
                if sieve[nmp] then
                    count += 1
                    if not bCountOnly then
                        res = append(res,sprintf("%2d: %2d+%2d+%2d = %d",
                                                 {count, n,  m,  p, nmp}))
                    end if
                end if
                if platform()!=JS and time()>t1 then
                    progress("Working... (%,d)\r",{count})
                    t1 = time()+1
                end if
            end for
        end for
    end for
    if platform()!=JS then progress("") end if
    string r = iff(bCountOnly?sprintf(" (%s)",{elapsed(time()-t0)})
                             :sprintf(":\n%s",{join(shorten(res,"",3),"\n")}))
    printf(1,"%,d strange triplets < %,d found%s\n\n",{count,lim,r})
end procedure
 
strange_triplets(30,false)
strange_triplets(1000)
strange_triplets(10000)
Output:
42 strange triplets < 30 found:
 1:  3+ 5+11 = 19
 2:  3+ 5+23 = 31
 3:  3+ 5+29 = 37
...
40: 13+19+29 = 61
41: 17+19+23 = 59
42: 19+23+29 = 71

241,580 strange triplets < 1,000 found (0.0s)

74,588,542 strange triplets < 10,000 found (11.4s)

Python[edit]

Using sympy.primerange.

from sympy import primerange
 
def strange_triplets(mx: int = 30) -> None:
primes = list(primerange(0, mx))
primes3 = set(primerange(0, 3 * mx))
for i, n in enumerate(primes):
for j, m in enumerate(primes[i + 1:], i + 1):
for p in primes[j + 1:]:
if n + m + p in primes3:
yield n, m, p
 
for c, (n, m, p) in enumerate(strange_triplets(), 1):
print(f"{c:2}: {n:2}+{m:2}+{p:2} = {n + m + p}")
 
mx = 1_000
print(f"\nIf n, m, p < {mx:_} finds {sum(1 for _ in strange_triplets(mx)):_}")
Output:
 1:  3+ 5+11 = 19
 2:  3+ 5+23 = 31
 3:  3+ 5+29 = 37
 4:  3+ 7+13 = 23
 5:  3+ 7+19 = 29
 6:  3+11+17 = 31
 7:  3+11+23 = 37
 8:  3+11+29 = 43
 9:  3+17+23 = 43
10:  5+ 7+11 = 23
11:  5+ 7+17 = 29
12:  5+ 7+19 = 31
13:  5+ 7+29 = 41
14:  5+11+13 = 29
15:  5+13+19 = 37
16:  5+13+23 = 41
17:  5+13+29 = 47
18:  5+17+19 = 41
19:  5+19+23 = 47
20:  5+19+29 = 53
21:  7+11+13 = 31
22:  7+11+19 = 37
23:  7+11+23 = 41
24:  7+11+29 = 47
25:  7+13+17 = 37
26:  7+13+23 = 43
27:  7+17+19 = 43
28:  7+17+23 = 47
29:  7+17+29 = 53
30:  7+23+29 = 59
31: 11+13+17 = 41
32: 11+13+19 = 43
33: 11+13+23 = 47
34: 11+13+29 = 53
35: 11+17+19 = 47
36: 11+19+23 = 53
37: 11+19+29 = 59
38: 13+17+23 = 53
39: 13+17+29 = 59
40: 13+19+29 = 61
41: 17+19+23 = 59
42: 19+23+29 = 71

If n, m, p < 1_000 finds 241_580

Raku[edit]

(formerly Perl 6)

# 20210312 Raku programming solution
 
for 30, 1000 -> \k {
given (2..k).grep(*.is-prime).combinations(3).grep(*.sum.is-prime) {
say "Found ", +$_, " strange unique prime triplets up to ", k
}
}
Output:
Found 42 strange unique prime triplets up to 30
Found 241580 strange unique prime triplets up to 1000

REXX[edit]

/*REXX program finds/lists triplet strange primes (<HI) where the triplets' sum is prime*/
parse arg hi . /*obtain optional argument from the CL.*/
if hi=='' | hi=="," then hi= 30 /*Not specified? Then use the default.*/
tell= hi>0; hi= abs(hi); hi= hi - 1 /*use absolute value of HI for limit. */
if tell>0 then say 'list of unique triplet strange primes whose sum is a prime.:'
call genP /*build array of semaphores for primes.*/
finds= 0 /*# of triplet strange primes (so far).*/
say
do m=2+1 by 2 to hi; if \!.m then iterate /*just use the odd primes. */
do n=m+2 by 2 to hi; if \!.n then iterate /* " " " " " */
mn= m + n /*partial sum (deep loops).*/
do p=n+2 by 2 to hi; if \!.p then iterate /*just use the odd primes. */
sum= mn + p /*compute sum of 3 primes. */
if \!.sum then iterate /*Is the sum prime? No, then skip it.*/
finds= finds + 1 /*bump # of triplet "strange" primes.*/
if tell then say right(m, w+9) right(n, w) right(p, w) ' sum to:' right(sum, w+2)
end /*p*/
end /*n*/
end /*m*/
say
say 'Found ' commas(finds) " unique triplet strange primes < " commas(hi+1) ,
" which sum to a prime."
exit 0 /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
commas: parse arg ?; do jc=length(?)-3 to 1 by -3; ?=insert(',', ?, jc); end; return ?
/*──────────────────────────────────────────────────────────────────────────────────────*/
genP: !.= 0; w= length(hi) /*semaphores for primes; width of #'s.*/
@.1=2; @.2=3; @.3=5; @.4=7; @.5=11 /*define some low primes. */
 !.2=1;  !.3=1;  !.5=1;  !.7=1;  !.11=1 /* " " " " semaphores. */
#=5; s.#= @.# **2 /*number of primes so far; prime². */
/* [↓] generate more primes ≤ high.*/
do [email protected].#+2 by 2 for hi*3%2 /*find odd primes from here on. */
parse var j '' -1 _; if _==5 then iterate /*J divisible by 5? (right dig)*/
if j// 3==0 then iterate /*" " " 3? */
if j// 7==0 then iterate /*" " " 7? */
/* [↑] the above five lines saves time*/
do k=5 while s.k<=j /* [↓] divide by the known odd primes.*/
if j // @.k == 0 then iterate j /*Is J ÷ X? Then not prime. ___ */
end /*k*/ /* [↑] only process numbers ≤ √ J */
#= #+1; @.#= j; s.#= j*j;  !.j= 1 /*bump # of Ps; assign next P; P²; P# */
end /*j*/; return
output   when using the default input:
list of unique triplet strange primes that sum to a prime:
prime generation took 0.02 seconds.

          3  5 11   sum to:    19
          3  5 23   sum to:    31
          3  5 29   sum to:    37
          3  7 13   sum to:    23
          3  7 19   sum to:    29
          3 11 17   sum to:    31
          3 11 23   sum to:    37
          3 11 29   sum to:    43
          3 17 23   sum to:    43
          5  7 11   sum to:    23
          5  7 17   sum to:    29
          5  7 19   sum to:    31
          5  7 29   sum to:    41
          5 11 13   sum to:    29
          5 13 19   sum to:    37
          5 13 23   sum to:    41
          5 13 29   sum to:    47
          5 17 19   sum to:    41
          5 19 23   sum to:    47
          5 19 29   sum to:    53
          7 11 13   sum to:    31
          7 11 19   sum to:    37
          7 11 23   sum to:    41
          7 11 29   sum to:    47
          7 13 17   sum to:    37
          7 13 23   sum to:    43
          7 17 19   sum to:    43
          7 17 23   sum to:    47
          7 17 29   sum to:    53
          7 23 29   sum to:    59
         11 13 17   sum to:    41
         11 13 19   sum to:    43
         11 13 23   sum to:    47
         11 13 29   sum to:    53
         11 17 19   sum to:    47
         11 19 23   sum to:    53
         11 19 29   sum to:    59
         13 17 23   sum to:    53
         13 17 29   sum to:    59
         13 19 29   sum to:    61
         17 19 23   sum to:    59
         19 23 29   sum to:    71

Found  42  unique triplet strange primes  <  30  which sum to a prime.
output   when using the input of:     -1000
Found  241,580  unique triplet strange primes  <  1,000  which sum to a prime.

Ring[edit]

 
load "stdlib.ring"
 
num = 0
limit = 30
 
see "working..." + nl
see "the strange primes are:" + nl
 
for n = 1 to limit
for m = n+1 to limit
for p = m+1 to limit
sum = n+m+p
if isprime(sum) and isprime(n) and isprime(m) and isprime(p)
num = num + 1
see "" + num + ": " + n + "+" + m + "+" + p + " = " + sum + nl
ok
next
next
next
 
see "done..." + nl
 
Output:
working...
the strange primes are:
1: 3+5+11 = 19
2: 3+5+23 = 31
3: 3+5+29 = 37
4: 3+7+13 = 23
5: 3+7+19 = 29
6: 3+11+17 = 31
7: 3+11+23 = 37
8: 3+11+29 = 43
9: 3+17+23 = 43
10: 5+7+11 = 23
11: 5+7+17 = 29
12: 5+7+19 = 31
13: 5+7+29 = 41
14: 5+11+13 = 29
15: 5+13+19 = 37
16: 5+13+23 = 41
17: 5+13+29 = 47
18: 5+17+19 = 41
19: 5+19+23 = 47
20: 5+19+29 = 53
21: 7+11+13 = 31
22: 7+11+19 = 37
23: 7+11+23 = 41
24: 7+11+29 = 47
25: 7+13+17 = 37
26: 7+13+23 = 43
27: 7+17+19 = 43
28: 7+17+23 = 47
29: 7+17+29 = 53
30: 7+23+29 = 59
31: 11+13+17 = 41
32: 11+13+19 = 43
33: 11+13+23 = 47
34: 11+13+29 = 53
35: 11+17+19 = 47
36: 11+19+23 = 53
37: 11+19+29 = 59
38: 13+17+23 = 53
39: 13+17+29 = 59
40: 13+19+29 = 61
41: 17+19+23 = 59
42: 19+23+29 = 71
done...

Rust[edit]

fn prime_sieve(limit: usize) -> Vec<bool> {
let mut sieve = vec![true; limit];
if limit > 0 {
sieve[0] = false;
}
if limit > 1 {
sieve[1] = false;
}
for i in (4..limit).step_by(2) {
sieve[i] = false;
}
let mut p = 3;
loop {
let mut q = p * p;
if q >= limit {
break;
}
if sieve[p] {
let inc = 2 * p;
while q < limit {
sieve[q] = false;
q += inc;
}
}
p += 2;
}
sieve
}
 
fn strange_unique_prime_triplets(limit: usize, verbose: bool) {
if limit < 6 {
return;
}
let mut primes = Vec::new();
let sieve = prime_sieve(limit * 3);
for p in (3..limit).step_by(2) {
if sieve[p] {
primes.push(p);
}
}
if verbose {
println!("Strange unique prime triplets < {}:", limit);
}
let mut count = 0;
let n = primes.len();
for i in 0..n - 2 {
for j in i + 1..n - 1 {
for k in j + 1..n {
let sum = primes[i] + primes[j] + primes[k];
if sieve[sum] {
count += 1;
if verbose {
println!(
"{:2} + {:2} + {:2} = {:2}",
primes[i], primes[j], primes[k], sum
);
}
}
}
}
}
println!(
"Count of strange unique prime triplets < {} is {}.",
limit, count
);
}
 
fn main() {
strange_unique_prime_triplets(30, true);
strange_unique_prime_triplets(1000, false);
}
Output:
Strange unique prime triplets < 30:
 3 +  5 + 11 = 19
 3 +  5 + 23 = 31
 3 +  5 + 29 = 37
 3 +  7 + 13 = 23
 3 +  7 + 19 = 29
 3 + 11 + 17 = 31
 3 + 11 + 23 = 37
 3 + 11 + 29 = 43
 3 + 17 + 23 = 43
 5 +  7 + 11 = 23
 5 +  7 + 17 = 29
 5 +  7 + 19 = 31
 5 +  7 + 29 = 41
 5 + 11 + 13 = 29
 5 + 13 + 19 = 37
 5 + 13 + 23 = 41
 5 + 13 + 29 = 47
 5 + 17 + 19 = 41
 5 + 19 + 23 = 47
 5 + 19 + 29 = 53
 7 + 11 + 13 = 31
 7 + 11 + 19 = 37
 7 + 11 + 23 = 41
 7 + 11 + 29 = 47
 7 + 13 + 17 = 37
 7 + 13 + 23 = 43
 7 + 17 + 19 = 43
 7 + 17 + 23 = 47
 7 + 17 + 29 = 53
 7 + 23 + 29 = 59
11 + 13 + 17 = 41
11 + 13 + 19 = 43
11 + 13 + 23 = 47
11 + 13 + 29 = 53
11 + 17 + 19 = 47
11 + 19 + 23 = 53
11 + 19 + 29 = 59
13 + 17 + 23 = 53
13 + 17 + 29 = 59
13 + 19 + 29 = 61
17 + 19 + 23 = 59
19 + 23 + 29 = 71
Count of strange unique prime triplets < 30 is 42.
Count of strange unique prime triplets < 1000 is 241580.

Swift[edit]

import Foundation
 
func primeSieve(limit: Int) -> [Bool] {
guard limit > 0 else {
return []
}
var sieve = Array(repeating: true, count: limit)
sieve[0] = false
if limit > 1 {
sieve[1] = false
}
if limit > 4 {
for i in stride(from: 4, to: limit, by: 2) {
sieve[i] = false
}
}
var p = 3
while true {
var q = p * p
if q >= limit {
break
}
if sieve[p] {
let inc = 2 * p
while q < limit {
sieve[q] = false
q += inc
}
}
p += 2
}
return sieve
}
 
func strangeUniquePrimeTriplets(limit: Int, verbose: Bool) {
guard limit > 5 else {
return;
}
let sieve = primeSieve(limit: 3 * limit)
var primes: [Int] = []
for p in stride(from: 3, to: limit, by: 2) {
if sieve[p] {
primes.append(p)
}
}
let n = primes.count
var count = 0
if verbose {
print("Strange unique prime triplets < \(limit):")
}
for i in (0..<n - 2) {
for j in (i + 1..<n - 1) {
for k in (j + 1..<n) {
let sum = primes[i] + primes[j] + primes[k]
if sieve[sum] {
count += 1
if verbose {
print(String(format: "%2d + %2d + %2d = %2d",
primes[i], primes[j], primes[k], sum))
}
}
}
}
}
print("\nCount of strange unique prime triplets < \(limit) is \(count).")
}
 
strangeUniquePrimeTriplets(limit: 30, verbose: true)
strangeUniquePrimeTriplets(limit: 1000, verbose: false)
Output:
Strange unique prime triplets < 30:
 3 +  5 + 11 = 19
 3 +  5 + 23 = 31
 3 +  5 + 29 = 37
 3 +  7 + 13 = 23
 3 +  7 + 19 = 29
 3 + 11 + 17 = 31
 3 + 11 + 23 = 37
 3 + 11 + 29 = 43
 3 + 17 + 23 = 43
 5 +  7 + 11 = 23
 5 +  7 + 17 = 29
 5 +  7 + 19 = 31
 5 +  7 + 29 = 41
 5 + 11 + 13 = 29
 5 + 13 + 19 = 37
 5 + 13 + 23 = 41
 5 + 13 + 29 = 47
 5 + 17 + 19 = 41
 5 + 19 + 23 = 47
 5 + 19 + 29 = 53
 7 + 11 + 13 = 31
 7 + 11 + 19 = 37
 7 + 11 + 23 = 41
 7 + 11 + 29 = 47
 7 + 13 + 17 = 37
 7 + 13 + 23 = 43
 7 + 17 + 19 = 43
 7 + 17 + 23 = 47
 7 + 17 + 29 = 53
 7 + 23 + 29 = 59
11 + 13 + 17 = 41
11 + 13 + 19 = 43
11 + 13 + 23 = 47
11 + 13 + 29 = 53
11 + 17 + 19 = 47
11 + 19 + 23 = 53
11 + 19 + 29 = 59
13 + 17 + 23 = 53
13 + 17 + 29 = 59
13 + 19 + 29 = 61
17 + 19 + 23 = 59
19 + 23 + 29 = 71

Count of strange unique prime triplets < 30 is 42.

Count of strange unique prime triplets < 1000 is 241580.

Visual Basic .NET[edit]

Translation of: C#
Imports DT = System.DateTime
 
Module Module1
 
Iterator Function Primes(lim As Integer) As IEnumerable(Of Integer)
Dim flags(lim) As Boolean
 
Dim j = 2
 
Dim d = 3
Dim sq = 4
While sq <= lim
If Not flags(j) Then
Yield j
For k = sq To lim Step j
flags(k) = True
Next
End If
 
j += 1
d += 2
sq += d
End While
 
While j <= lim
If Not flags(j) Then
Yield j
End If
j += 1
End While
End Function
 
Sub Main()
For Each lmt In {90, 300, 3000, 30000, 111000}
Dim pr = Primes(lmt).Skip(1).ToList()
Dim st = DT.Now
Dim f = 0
Dim r As New List(Of String)
Dim i = -1
Dim m = lmt \ 3
Dim h = m
While i < 0
i = pr.IndexOf(h)
h -= 1
End While
Dim j = i - 1
Dim k = j - 1
For a = 0 To k
Dim pra = pr(a)
For b = a + 1 To j
Dim prab = pra + pr(b)
For c = b + 1 To i
Dim d = prab + pr(c)
If Not pr.Contains(d) Then
Continue For
End If
f += 1
If lmt < 100 Then
r.Add(String.Format("{3,5} = {0,2} + {1,2} + {2,2}", pra, pr(b), pr(c), d))
End If
Next
Next
Next
Dim s = "s.u.p.t.s under "
r.Sort()
If r.Count > 0 Then
Console.WriteLine("{0}{1}:" + vbNewLine + "{2}", s, m, String.Join(vbNewLine, r))
End If
If lmt > 100 Then
Console.WriteLine("Count of {0}{1,6:n0}: {2,13:n0} {3} sec", s, m, f, (DT.Now - st).ToString().Substring(6))
End If
Next
End Sub
 
End Module
Output:
Same as C#

Wren[edit]

Basic[edit]

Library: Wren-math
Library: Wren-trait
Library: Wren-fmt
import "/math" for Int
import "/trait" for Stepped
import "/fmt" for Fmt
 
var strangePrimes = Fn.new { |n, countOnly|
var c = 0
var s
for (i in Stepped.new(3..n-4, 2)) {
if (Int.isPrime(i)) {
for (j in Stepped.new(i+2..n-2, 2)) {
if (Int.isPrime(j)) {
for (k in Stepped.new(j+2..n, 2)) {
if (Int.isPrime(k) && Int.isPrime(s = i + j + k)) {
c = c + 1
if (!countOnly) Fmt.print("$2d: $2d + $2d + $2d = $2d", c, i, j, k, s)
}
}
}
}
}
}
return c
}
 
System.print("Unique prime triples under 30 which sum to a prime:")
strangePrimes.call(29, false)
var c = strangePrimes.call(999, true)
Fmt.print("\nThere are $,d unique prime triples under 1,000 which sum to a prime.", c)
Output:
Unique prime triples under 30 which sum to a prime:
 1:  3 +  5 + 11 = 19
 2:  3 +  5 + 23 = 31
 3:  3 +  5 + 29 = 37
 4:  3 +  7 + 13 = 23
 5:  3 +  7 + 19 = 29
 6:  3 + 11 + 17 = 31
 7:  3 + 11 + 23 = 37
 8:  3 + 11 + 29 = 43
 9:  3 + 17 + 23 = 43
10:  5 +  7 + 11 = 23
11:  5 +  7 + 17 = 29
12:  5 +  7 + 19 = 31
13:  5 +  7 + 29 = 41
14:  5 + 11 + 13 = 29
15:  5 + 13 + 19 = 37
16:  5 + 13 + 23 = 41
17:  5 + 13 + 29 = 47
18:  5 + 17 + 19 = 41
19:  5 + 19 + 23 = 47
20:  5 + 19 + 29 = 53
21:  7 + 11 + 13 = 31
22:  7 + 11 + 19 = 37
23:  7 + 11 + 23 = 41
24:  7 + 11 + 29 = 47
25:  7 + 13 + 17 = 37
26:  7 + 13 + 23 = 43
27:  7 + 17 + 19 = 43
28:  7 + 17 + 23 = 47
29:  7 + 17 + 29 = 53
30:  7 + 23 + 29 = 59
31: 11 + 13 + 17 = 41
32: 11 + 13 + 19 = 43
33: 11 + 13 + 23 = 47
34: 11 + 13 + 29 = 53
35: 11 + 17 + 19 = 47
36: 11 + 19 + 23 = 53
37: 11 + 19 + 29 = 59
38: 13 + 17 + 23 = 53
39: 13 + 17 + 29 = 59
40: 13 + 19 + 29 = 61
41: 17 + 19 + 23 = 59
42: 19 + 23 + 29 = 71

There are 241,580 unique prime triples under 1,000 which sum to a prime.

Faster[edit]

The following version uses a prime sieve and is about 17 times faster than the 'basic' version.

import "/math" for Int
import "/fmt" for Fmt
 
var max = 1000
var sieved = Int.primeSieve(3*max, false) // includes composites
var p = Int.primeSieve(max, true) // primes only
 
var strangePrimes = Fn.new { |n, countOnly|
var c = 0
var m = 0
while (m < p.count && p[m] <= n) m = m + 1
var r
var s
for (i in 1...m-2) {
for (j in i+1...m-1) {
r = p[i] + p[j]
for (k in j+1...m) {
if (!sieved[s = r + p[k]]) {
c = c + 1
if (!countOnly) Fmt.print("$2d: $2d + $2d + $2d = $2d", c, p[i], p[j], p[k], s)
}
}
}
}
return c
}
 
System.print("Unique prime triples under 30 which sum to a prime:")
strangePrimes.call(29, false)
var c = strangePrimes.call(999, true)
Fmt.print("\nThere are $,d unique prime triples under 1,000 which sum to a prime.", c)
Output:

Same as 'basic' version.