A023245 Primes that remain prime through 2 iterations of the function f(x) = 2x + 9.

5, 11, 19, 31, 59, 61, 71, 101, 109, 151, 179, 239, 241, 269, 281, 389, 409, 439, 449, 521, 571, 641, 659, 719, 829, 911, 971, 1051, 1061, 1181, 1201, 1229, 1319, 1361, 1439, 1579, 1669, 1699, 1741, 1831, 1949, 2269, 2341, 2371, 2521, 2549, 2579, 2609, 2671

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

Primes p such that 2*p+9 and 4*n+27 are also primes. - Vincenzo Librandi, Aug 04 2010

Links

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

Crossrefs

Subsequence of A023207 and A155722.

Programs

Magma

[n: n in [0..100000] | IsPrime(n) and IsPrime(2*n+9) and IsPrime(4*n+27)] // Vincenzo Librandi, Aug 04 2010

Mathematica

Select[Prime[Range[500]],And@@PrimeQ[Rest[NestList[2#+9&,#,2]]]&]  (* Harvey P. Dale, Mar 23 2011 *)

PARI

isok(n) = isprime(n) && isprime(2*n+9) && isprime(4*n+27); \\ Michel Marcus, Sep 12 2016