Double Twin Primes
Definition
Let (p1,p2) and (p3,p4) be twin primes where p3 - p2 = 4.
Such primes called Double Twin Primes
Example
[5,7,11,13]
Task
Find and show here all Double Twin Primes under 1000.
Ring
see "works..." + nl
primes = []
limit = 1000
for n =1 to limit/2
if isPrime(n)
add(primes,n)
ok
next
lenPrimes = len(primes)-3
for m = 1 to lenPrimes
if isPrime(primes[m]) and isPrime(primes[m+1]) and
isPrime(primes[m+2]) and isPrime(primes[m+3])
if (primes[m+1] - primes[m] = 2) and (primes[m+2] - primes[m+1] = 4) and
(primes[m+3] - primes[m+2] = 2)
see " " + primes[m]+ " " + primes[m+1] + " " +
primes[m+2] + " " + primes[m+3] + nl
ok
ok
next
see "done..." + nl
func isPrime num
if (num <= 1) return 0 ok
if (num % 2 = 0 and num != 2) return 0 ok
for i = 3 to floor(num / 2) -1 step 2
if (num % i = 0) return 0 ok
next
return 1
- Output:
works... 5 7 11 13 11 13 17 19 101 103 107 109 191 193 197 199 done...