A023235 Primes p such that 9*p + 8 is also prime.

5, 7, 11, 19, 29, 47, 61, 71, 79, 89, 97, 107, 127, 131, 139, 151, 167, 179, 181, 211, 229, 251, 271, 317, 337, 397, 401, 419, 421, 449, 461, 467, 487, 541, 547, 557, 571, 599, 601, 607, 659, 677, 701, 709, 727, 739, 761, 811, 827, 839, 877, 881, 907, 929, 971, 1051

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• easy

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Programs

Magma

[n: n in [0..1000] | IsPrime(n) and IsPrime(9*n+8)]; // Vincenzo Librandi, Nov 20 2010

Magma

[p: p in PrimesUpTo(1100)| IsPrime(9*p+8)]; // Vincenzo Librandi, May 21 2014

Mathematica

lst={};Do[p=Prime[n];If[PrimeQ[9*p+8],AppendTo[lst,p]],{n,6!}];lst (* Vladimir Joseph Stephan Orlovsky, Mar 10 2009 *)
Select[Prime[Range[900]], PrimeQ[9 # + 8] &] (* Vincenzo Librandi, May 21 2014 *)

PARI

is(n)=isprime(9*n+8) && isprime(n) \\ Charles R Greathouse IV, Jul 02 2013