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 A364045 #12 Jul 05 2023 01:44:35
%S A364045 0,0,1,0,0,1,0,-1,1,0,0,1,1,0,1,-1,0,0,0,0,1,0,1,0,0,1,1,-1,0,1,0,-1,
%T A364045 2,0,0,0,0,-1,2,-1,0,1,1,0,1,1,0,-1,0,0,1,1,1,0,0,-2,1,-1,0,1,0,0,2,
%U A364045 -1,1,2,0,-1,2,0,0,-1,1,0,1,-1,0,1,0,-1,1,0,1,0,0,1,1,-2,0,0,1,1,2,0,0,-1,0,-1,2,0,0,1
%N A364045 Expansion of Sum_{k>0} x^(3*k) / (1 + x^(5*k)).
%F A364045 G.f.: Sum_{k>0} (-1)^(k-1) * x^(5*k-2) / (1 - x^(5*k-2)).
%F A364045 a(n) = -Sum_{d|n, d==3 (mod 5)} (-1)^d.
%t A364045 a[n_] := -DivisorSum[n, (-1)^# &, Mod[#, 5] == 3 &]; Array[a, 100] (* _Amiram Eldar_, Jul 05 2023 *)
%o A364045 (PARI) a(n) = -sumdiv(n, d, (d%5==3)*(-1)^d);
%Y A364045 Cf. A364043, A364044, A364046.
%Y A364045 Cf. A001878, A364021.
%K A364045 sign
%O A364045 1,33
%A A364045 _Seiichi Manyama_, Jul 03 2023