A023255 Primes that remain prime through 2 iterations of the function f(x) = 5x + 8.

7, 13, 19, 31, 43, 73, 211, 223, 241, 307, 397, 409, 631, 661, 727, 757, 769, 829, 883, 1123, 1741, 1783, 1867, 2131, 2143, 2269, 2287, 2467, 2521, 2551, 2857, 2917, 3253, 3319, 3793, 3967, 4297, 4423, 4597, 4957, 5449, 5563, 5701, 6229, 6427, 6469, 6679

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

Primes p such that 5*p+8 and 25*p+48 are also primes. - Vincenzo Librandi, Aug 04 2010

Links

• John Cerkan, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A023220, A111225.

Programs

Magma

[n: n in [0..100000] | IsPrime(n) and IsPrime(5*n+8) and IsPrime(25*n+48)] // Vincenzo Librandi, Aug 04 2010

Mathematica

fQ[n_]:=And@@PrimeQ[NestList[5#+8&,n,2]]; Select[Range[7000],fQ] (* Harvey P. Dale, Mar 25 2013 *)

Formula

a(n) == 1 (mod 6). - John Cerkan, Sep 14 2016