A139487 - OEIS

%I #33 Feb 03 2024 00:51:22

%S 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,

%T 62,74,75,78,80,89,90,92,93,102,104,107,110,113,114,120,122,123,128,

%U 129,132,135,137,143,152,153,159,162,164,165,170,174,177,179,180,183,185

%N Numbers k such that 8k + 7 is prime.

%C For numbers k such that:

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

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

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

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

%C 8k + 7 divides A000225(4k+3). - _Jinyuan Wang_, Mar 08 2019

%H Vincenzo Librandi, <a href="/A139487/b139487.txt">Table of n, a(n) for n = 1..1000</a>

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

%t a = {}; Do[If[PrimeQ[8 n + 7], AppendTo[a, n]], {n, 0, 300}]; a

%t Select[Range[0,200],PrimeQ[8#+7]&] (* _Harvey P. Dale_, Oct 10 2012 *)

%o (Magma) [n: n in [0..200] | IsPrime(8*n+7)]; // _Vincenzo Librandi_, Jun 25 2014

%o (PARI) is(n)=isprime(8*n+7) \\ _Charles R Greathouse IV_, Feb 17 2017

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

%K nonn,easy

%O 1,2

%A _Artur Jasinski_, Apr 23 2008