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 A364046 #10 Jul 03 2023 11:46:02
%S A364046 0,0,0,1,0,0,0,1,-1,0,0,1,0,1,0,1,0,-1,-1,1,0,0,0,2,0,0,-1,2,-1,0,0,1,
%T A364046 0,1,0,0,0,-1,-1,1,0,1,0,2,-1,0,0,2,-1,0,0,1,0,0,0,2,-1,-1,-1,1,0,0,
%U A364046 -1,2,0,0,0,2,-1,1,0,1,0,1,0,0,0,-1,-1,1,-1,0,0,3,0,0,-1,2,-1,-1,0,1,0,1,-1,2,0,0,-2
%N A364046 Expansion of Sum_{k>0} x^(4*k) / (1 + x^(5*k)).
%F A364046 G.f.: Sum_{k>0} (-1)^(k-1) * x^(5*k-1) / (1 - x^(5*k-1)).
%F A364046 a(n) = Sum_{d|n, d==4 (mod 5)} (-1)^d.
%t A364046 a[n_] := DivisorSum[n, (-1)^# &, Mod[#, 5] == 4 &]; Array[a, 100] (* _Amiram Eldar_, Jul 03 2023 *)
%o A364046 (PARI) a(n) = sumdiv(n, d, (d%5==4)*(-1)^d);
%Y A364046 Cf. A364043, A364044, A364045.
%Y A364046 Cf. A001899, A364022.
%K A364046 sign
%O A364046 1,24
%A A364046 _Seiichi Manyama_, Jul 03 2023