A023264 Primes that remain prime through 2 iterations of function f(x) = 8x + 9.

23, 43, 83, 109, 193, 379, 389, 569, 643, 659, 853, 1063, 1129, 1283, 1423, 1493, 1759, 1789, 1889, 2003, 2129, 2293, 2459, 2713, 2729, 2879, 2969, 3373, 3823, 4519, 4603, 4649, 4663, 4703, 4783, 4789, 5023, 5153, 5209, 5639, 5653, 5669, 5693, 5783, 6203

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

Primes p such that 8*p+9 and 64*p+81 are also primes. - Vincenzo Librandi, Aug 04 2010

Links

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

Crossrefs

Subsequence of A023232 and of A153762.

Programs

Magma

[n: n in [1..100000] | IsPrime(n) and IsPrime(8*n+9) and IsPrime(64*n+81)] // Vincenzo Librandi, Aug 04 2010

Mathematica

Select[Prime[Range[1000]],AllTrue[Rest[NestList[8#+9&,#,2]],PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Sep 26 2016 *)

Formula

a(n) == 3 or 9 (mod 10). - John Cerkan, Sep 16 2016