Sum of primes in odd positions is prime: Difference between revisions

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load "stdlib.ring"
load "stdlib.ring"
see "working..." + nl
see "working..." + nl
see "p" + " sum" + nl
see "i p sum" + nl


nr = 0
nr = 0
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sum += n
sum += n
if isprime(sum)
if isprime(sum)
see "" + n + " " + sum + nl
see "" + nr + " " + n + " " + sum + nl
ok
ok
ok
ok
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<pre>
<pre>
working...
working...
p sum
i p sum
2 2
1 2 2
5 7
3 5 7
31 89
11 31 89
103 659
27 103 659
149 1181
35 149 1181
331 5021
67 331 5021
467 9923
91 467 9923
499 10909
95 499 10909
523 11941
99 523 11941
653 17959
119 653 17959
823 26879
143 823 26879
done...
done...
</pre>
</pre>

Revision as of 15:03, 1 September 2021

Sum of primes in odd positions is prime 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.
Task


Let p(i) be a sequence of prime numbers.
Consider the p(1),p(3),p(5), ... ,p(i), for each p(i) < 1,000 and i is odd.
Let sum be the sum of these primes.
If sum is prime then print p(i) and sum.



Factor

Works with: Factor version 0.99 2021-06-02

<lang factor>USING: assocs assocs.extras kernel math.primes math.statistics prettyprint sequences.extras ;

1000 primes-upto <evens> dup cum-sum zip [ prime? ] filter-values .</lang>

Output:
{
    { 2 2 }
    { 5 7 }
    { 31 89 }
    { 103 659 }
    { 149 1181 }
    { 331 5021 }
    { 467 9923 }
    { 499 10909 }
    { 523 11941 }
    { 653 17959 }
    { 823 26879 }
}

Go

Translation of: Wren
Library: Go-rcu

<lang go>package main

import (

   "fmt"
   "rcu"

)

func main() {

   primes := rcu.Primes(999)
   sum := 0
   fmt.Println(" i   p[i]  Σp[i]")
   fmt.Println("----------------")
   for i := 0; i < len(primes); i += 2 {
       sum += primes[i]
       if rcu.IsPrime(sum) {
           fmt.Printf("%3d  %3d  %6s\n", i+1, primes[i], rcu.Commatize(sum))
       }
   }

}</lang>

Output:
 i   p[i]  Σp[i]
----------------
  1    2       2
  3    5       7
 11   31      89
 27  103     659
 35  149   1,181
 67  331   5,021
 91  467   9,923
 95  499  10,909
 99  523  11,941
119  653  17,959
143  823  26,879

Raku

<lang perl6>my @odd = grep { ++$ !%% 2 }, grep &is-prime, 2 ..^ 1000; my @sums = [\+] @odd;

say .fmt('%5d') for grep { .[1].is-prime }, ( @odd Z @sums );</lang>

Output:
  2     2
  5     7
 31    89
103   659
149  1181
331  5021
467  9923
499 10909
523 11941
653 17959
823 26879

Ring

<lang ring> load "stdlib.ring" see "working..." + nl see "i p sum" + nl

nr = 0 sum = 0 limit = 1000

for n = 2 to limit

   if isprime(n)
      nr++
      if nr%2 = 1
         sum += n
         if isprime(sum)
            see "" + nr + " " + n + " " + sum + nl
         ok
      ok
   ok

next

see "done..." + nl </lang>

Output:
working...
i p sum
1 2 2
3 5 7
11 31 89
27 103 659
35 149 1181
67 331 5021
91 467 9923
95 499 10909
99 523 11941
119 653 17959
143 823 26879
done...

Wren

Library: Wren-math
Library: Wren-trait
Library: Wren-fmt

<lang ecmascript>import "/math" for Int import "/trait" for Indexed import "/fmt" for Fmt

var primes = Int.primeSieve(999) var sum = 0 System.print(" i p[i] Σp[i]") System.print("----------------") for (se in Indexed.new(primes, 2)) {

   sum = sum + se.value
   if (Int.isPrime(sum)) Fmt.print("$3d  $3d  $,6d", se.index + 1, se.value, sum)

}</lang>

Output:
 i   p[i]  Σp[i]
----------------
  1    2       2
  3    5       7
 11   31      89
 27  103     659
 35  149   1,181
 67  331   5,021
 91  467   9,923
 95  499  10,909
 99  523  11,941
119  653  17,959
143  823  26,879

XPL0

<lang XPL0>func IsPrime(N); \Return 'true' if N is a prime number int N, I; [if N <= 1 then return false; for I:= 2 to sqrt(N) do

   if rem(N/I) = 0 then return false;

return true; ];

int I, Sum, N; [Text(0, "p(n) sum^m^j"); Sum:= 0; I:= 0; for N:= 2 to 1000-1 do

   [if IsPrime(N) then
       [I:= I+1;
       if I&1 then     \odd
           [Sum:= Sum + N;
           if IsPrime(Sum) then
               [IntOut(0, N);  ChOut(0, ^      );  IntOut(0, Sum);  CrLf(0)];
           ];
       ];
   ];

]</lang>

Output:
p(n)    sum
2       2
5       7
31      89
103     659
149     1181
331     5021
467     9923
499     10909
523     11941
653     17959
823     26879