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 A363037 #25 Jul 03 2023 00:53:14
%S A363037 1,1,1,1,0,1,1,1,2,0,1,1,0,1,0,1,2,2,1,0,0,1,1,1,1,0,2,1,0,0,1,1,2,2,
%T A363037 0,2,0,1,0,0,2,0,1,1,0,1,1,1,2,1,2,0,0,2,0,1,2,0,1,0,0,1,1,1,0,2,1,2,
%U A363037 0,0,1,2,2,0,1,1,0,0,1,0,3,2,1,0,0,1,0,1,2,0,0,1,0,1,0,1,2,2,3,1,0,2,1,0,0
%N A363037 Expansion of Sum_{k>0} x^k / (1 + x^(4*k)).
%F A363037 G.f.: Sum_{k>0} (-1)^(k-1) * x^(4*k-3) / (1 - x^(4*k-3)).
%F A363037 a(n) = Sum_{d|n, d==1 (mod 4)} (-1)^((d-1)/4).
%t A363037 a[n_] := DivisorSum[n, (-1)^((# - 1)/4) &, Mod[#, 4] == 1 &]; Array[a, 100] (* _Amiram Eldar_, Jul 03 2023 *)
%o A363037 (PARI) a(n) = sumdiv(n, d, (d%4==1)*(-1)^((d-1)/4));
%Y A363037 Cf. A002654, A364011.
%Y A363037 Cf. A364031, A364032.
%K A363037 nonn
%O A363037 1,9
%A A363037 _Seiichi Manyama_, Jul 01 2023