A023246 Primes that remain prime through 2 iterations of the function f(x) = 3*x + 2.

5, 7, 19, 29, 79, 89, 97, 127, 139, 167, 317, 337, 397, 419, 607, 659, 709, 877, 929, 1069, 1129, 1409, 1699, 1777, 2029, 2099, 2267, 2339, 2557, 2617, 2707, 2837, 2917, 2939, 3019, 3067, 3389, 3407, 3529, 3617, 3659, 3719, 4229, 4549, 4919, 5209, 5227, 5417

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

Primes p such that 3*p+2 and 9*p+8 are also primes. - Vincenzo Librandi, Aug 04 2010

All terms after the first == 7 or 9 (mod 10). - Robert Israel, Sep 12 2016

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A023208.

Programs

Magma

[n: n in [0..100000] | IsPrime(n) and IsPrime(3*n+2) and IsPrime(9*n+8)] // Vincenzo Librandi, Aug 04 2010

Maple

select(t -> isprime(t) and isprime(3*t+2) and isprime(9*t+8), [5, seq(seq(10*i+j,j=[7,9]),i=0..10^4)]); # Robert Israel, Sep 12 2016

Mathematica

Select[Prime[Range[750]],And@@PrimeQ[Rest[NestList[3#+2&,#,2]]]&] (* Harvey P. Dale, May 05 2014 *)