A023218 Primes p such that 5*p + 4 is also prime.

3, 5, 11, 17, 29, 47, 53, 71, 83, 89, 101, 113, 131, 167, 251, 257, 263, 281, 311, 389, 419, 461, 467, 479, 491, 509, 521, 557, 563, 587, 593, 599, 617, 641, 659, 677, 743, 797, 809, 827, 857, 881, 929, 977, 983, 1019, 1061, 1103, 1187, 1217, 1259, 1277, 1289, 1319

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• easy

Comments

Except for the first term, all terms are congruent to 5 (mod 6). - John Cerkan, Sep 07 2016

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..2000

Crossrefs

Subsequence of primes of A024897.

Programs

Magma

[n: n in [0..1000] | IsPrime(n) and IsPrime(5*n+4)]; // Vincenzo Librandi, Nov 20 2010

Maple

A023218:=n->`if`(isprime(n) and isprime(5*n+4), n, NULL): seq(A023218(n), n=1..2*10^3); # Wesley Ivan Hurt, Sep 07 2016

Mathematica

lst={};Do[If[PrimeQ[n]&&PrimeQ[5*n+4], AppendTo[lst, n]], {n, 13^3}];lst (* Vladimir Joseph Stephan Orlovsky, Sep 08 2008 *)
Select[Prime[Range[300]],PrimeQ[5#+4]&] (* Harvey P. Dale, Dec 31 2013 *)