A023215 Primes p such that 4*p + 7 is also prime.

3, 13, 19, 31, 43, 61, 103, 109, 139, 163, 241, 271, 313, 373, 379, 499, 523, 601, 613, 631, 643, 673, 709, 733, 739, 751, 769, 811, 823, 829, 883, 1021, 1033, 1051, 1063, 1069, 1129, 1171, 1231, 1249, 1291, 1381, 1459, 1483, 1531, 1549, 1579, 1621, 1663

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• easy

Comments

Except for the first term, all terms are congruent to 1 (mod 6). - John Cerkan, Sep 07 2016

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Subsequence of primes of A089986.

Programs

Magma

[n: n in PrimesUpTo(500) | IsPrime(4*n+7)]; // Vincenzo Librandi, Nov 19 2010

Maple

A023215:=n->`if`(isprime(n) and isprime(4*n+7), n, NULL): seq(A023215(n), n=1..3*10^3); # Wesley Ivan Hurt, Sep 07 2016

Mathematica

Select[Prime[Range[300]],PrimeQ[4#+7]&] (* Harvey P. Dale, Jan 21 2011 *)