This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A120309 #13 Jul 20 2024 17:23:11
%S A120309 1,7,8,9,10,19,20,21,22,37,38,39,40,53,54,55,56,57,58,71,72,89,90,91,
%T A120309 92,93,94,95,96,107,108,131,132,133,134,135,136,151,152,153,154,155,
%U A120309 156,173,174,175,176,177,178,193,194,195,196
%N A120309 Numbers k such that pi(k) == 0 (mod 4), where pi() = A000720.
%t A120309 a = Flatten[Table[If[Mod[PrimePi[n], 4] == 0, n, {}], {n, 1, 200}]]
%t A120309 Select[Range[200],Mod[PrimePi[#],4]==0&] (* _Harvey P. Dale_, Jul 20 2024 *)
%o A120309 (PARI) isok(k) = (primepi(k) % 4) == 0; \\ _Michel Marcus_, Feb 09 2021
%Y A120309 Cf. A000720.
%K A120309 nonn
%O A120309 1,2
%A A120309 _Roger L. Bagula_, Jun 20 2006
%E A120309 Edited by _N. J. A. Sloane_, Jul 22 2006