A023206 Numbers m such that m and 2*m + 7 both prime.

2, 3, 5, 11, 17, 23, 41, 47, 53, 71, 83, 113, 131, 137, 173, 191, 197, 227, 251, 257, 281, 293, 317, 347, 383, 401, 461, 467, 503, 521, 587, 593, 641, 647, 677, 683, 701, 743, 773, 797, 857, 863, 941, 947, 953, 971, 983, 1031, 1061, 1103, 1151, 1163, 1187, 1193, 1217

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• easy

Comments

Subsequence of A105760. Except for the first two terms, all terms are congruent to 5 mod 6. - John Cerkan, Sep 07 2016

Links

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

Crossrefs

Cf. A005384, A023204, A023205.

Programs

Magma

[n: n in [0..1000] | IsPrime(n) and IsPrime(2*n+7)]; // Vincenzo Librandi, Nov 20 2010

Maple

A023206:=n->`if`(isprime(n) and isprime(2*n+7), n, NULL): seq(A023206(n), n=1..3*1000); # Wesley Ivan Hurt, Sep 07 2016

Mathematica

Select[Prime@Range@250,PrimeQ[2#+7]&] (* Vladimir Joseph Stephan Orlovsky, Apr 25 2011 *)

PARI

is(n)=isprime(2*n+7) && isprime(n) \\ Charles R Greathouse IV, Sep 07 2016