A023205 Numbers m such that m and 2*m + 5 are both prime.

3, 7, 13, 19, 31, 37, 61, 67, 73, 79, 97, 103, 109, 139, 151, 163, 181, 229, 241, 271, 283, 307, 313, 367, 373, 409, 439, 457, 523, 541, 613, 643, 661, 709, 727, 733, 739, 769, 787, 811, 829, 859, 877, 937, 991, 997, 1039, 1063, 1069, 1087, 1117, 1123, 1153, 1171

Offset: 1

Author

David W. Wilson, Jun 14 1998

Keywords

• nonn

Links

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

Crossrefs

Subsequence of primes of A089038.

Cf. A005384, A023204.

Programs

Magma

[n: n in [0..100000] | IsPrime(n) and IsPrime(2*n+5)] // Vincenzo Librandi, Aug 04 2010

Maple

A023205:=n->`if`(isprime(n) and isprime(2*n+5), n, NULL): seq(A023205(n), n=1..3*10^3); # Wesley Ivan Hurt, Sep 08 2016

Mathematica

Select[Prime@Range@250, PrimeQ[2#+5]&] (* Vladimir Joseph Stephan Orlovsky, Apr 25 2011 *)

Formula

a(n) == 1 (mod 6) for n>=2. - John Cerkan, Sep 07 2016