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 A363617 #18 Jul 19 2023 02:19:53
%S A363617 0,0,1,-4,10,-19,35,-60,85,-110,165,-243,286,-329,466,-620,680,-751,
%T A363617 969,-1254,1366,-1375,1771,-2323,2310,-2314,3010,-3609,3654,-3734,
%U A363617 4495,-5580,5622,-5304,6590,-8115,7770,-7467,9426,-11190,10660,-10498,12341,-14623,14740,-13409,16215,-20179,18459,-17410,21506
%N A363617 Expansion of Sum_{k>0} x^(3*k)/(1+x^k)^4.
%H A363617 Seiichi Manyama, <a href="/A363617/b363617.txt">Table of n, a(n) for n = 1..10000</a>
%F A363617 G.f.: -Sum_{k>0} binomial(k,3) * (-x)^k/(1 - x^k).
%F A363617 a(n) = -Sum_{d|n} (-1)^d * binomial(d,3).
%t A363617 a[n_] := -DivisorSum[n, (-1)^#*Binomial[#, 3] &]; Array[a, 50] (* _Amiram Eldar_, Jul 18 2023 *)
%o A363617 (PARI) my(N=60, x='x+O('x^N)); concat([0, 0], Vec(sum(k=1, N, x^(3*k)/(1+x^k)^4)))
%o A363617 (PARI) a(n) = -sumdiv(n, d, (-1)^d*binomial(d, 3));
%Y A363617 Cf. A363022, A363618.
%Y A363617 Cf. A363607.
%K A363617 sign
%O A363617 1,4
%A A363617 _Seiichi Manyama_, Jun 11 2023