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 A363598 #26 Jul 25 2023 17:18:51
%S A363598 0,1,-4,11,-20,32,-56,95,-124,146,-220,328,-364,400,-584,775,-816,881,
%T A363598 -1140,1486,-1600,1552,-2024,2712,-2620,2562,-3400,4064,-4060,4112,
%U A363598 -4960,6231,-6208,5730,-7216,8947,-8436,8000,-10248,12230,-11480,11232,-13244,15752
%N A363598 Expansion of Sum_{k>0} x^(2*k)/(1+x^k)^4.
%H A363598 Seiichi Manyama, <a href="/A363598/b363598.txt">Table of n, a(n) for n = 1..10000</a>
%F A363598 G.f.: Sum_{k>0} binomial(k+1,3) * (-x)^k/(1 - x^k).
%F A363598 a(n) = Sum_{d|n} (-1)^d * binomial(d+1,3) = (A002129(n) - A138503(n))/6.
%t A363598 a[n_] := DivisorSum[n, (-1)^# * Binomial[# + 1, 3] &]; Array[a, 50] (* _Amiram Eldar_, Jul 25 2023 *)
%o A363598 (PARI) my(N=50, x='x+O('x^N)); concat(0, Vec(sum(k=1, N, x^(2*k)/(1+x^k)^4)))
%o A363598 (PARI) a(n) = sumdiv(n, d, (-1)^d*binomial(d+1, 3));
%Y A363598 Cf. A325940, A363022, A363613, A363614.
%Y A363598 Cf. A002129, A138503, A363604.
%K A363598 sign
%O A363598 1,3
%A A363598 _Seiichi Manyama_, Jun 11 2023