A296020 - OEIS

%I #15 Aug 10 2019 13:24:21

%S 1,2,3,3,4,5,5,6,6,6,7,8,8,8,9,9,10,11,11,12,13,13,13,13,13,14,15,15,

%T 15,15,15,16,17,17,18,18,18,19,19,19,20,21,21,21,22,22,22,23,23,24,24,

%U 24,25,25,25,26,27,27,27,28,28,28,29,29,29,30,30,31,31,31

%N Number of primes of the form 4*k+3 <= 4*n+3.

%H Seiichi Manyama, <a href="/A296020/b296020.txt">Table of n, a(n) for n = 0..10000</a>

%t Module[{nn=300,pr3},pr3=Table[If[PrimeQ[k]&&Mod[k,4]==3,1,0],{k,0,nn}];Table[Total[Take[pr3,4n+3]],{n,(nn-3)/4}]] (* _Harvey P. Dale_, Aug 10 2019 *)

%o (Ruby)

%o require 'prime'

%o def A(k, n)

%o   ary = []

%o   cnt = 0

%o   k.step(4 * n + k, 4){|i|

%o     cnt += 1 if i.prime?

%o     ary << cnt

%o   }

%o   ary

%o end

%o p A(3, 100)

%Y Cf. A004767, A091099, A295996, A296021.

%K nonn

%O 0,2

%A _Seiichi Manyama_, Dec 02 2017