A139487 Numbers k such that 8k + 7 is prime.

0, 2, 3, 5, 8, 9, 12, 15, 18, 20, 23, 24, 27, 29, 32, 33, 38, 44, 45, 47, 53, 54, 57, 59, 60, 62, 74, 75, 78, 80, 89, 90, 92, 93, 102, 104, 107, 110, 113, 114, 120, 122, 123, 128, 129, 132, 135, 137, 143, 152, 153, 159, 162, 164, 165, 170, 174, 177, 179, 180, 183, 185

Offset: 1

Author

Artur Jasinski, Apr 23 2008

Keywords

• nonn
• easy

Comments

For numbers k such that:

8k+1 is prime see A005123, primes see A007519;

8k+3 is prime see A005124, primes see A007520;

8k+5 is prime see A105133, primes see A007521;

8k+7 is prime see A139487, primes see A007522.

8k + 7 divides A000225(4k+3). - Jinyuan Wang, Mar 08 2019

Links

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

Crossrefs

Cf. A000225, A007519, A007520, A007521, A007522, A005123, A005124, A105133.

Programs

Magma

[n: n in [0..200] | IsPrime(8*n+7)]; // Vincenzo Librandi, Jun 25 2014

Mathematica

a = {}; Do[If[PrimeQ[8 n + 7], AppendTo[a, n]], {n, 0, 300}]; a
Select[Range[0,200],PrimeQ[8#+7]&] (* Harvey P. Dale, Oct 10 2012 *)

PARI

is(n)=isprime(8*n+7) \\ Charles R Greathouse IV, Feb 17 2017

Formula

a(n) = (A007522(n) - 7)/8, n >= 1.