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 A363604 #31 Dec 30 2024 02:16:14
%S A363604 0,1,4,11,20,40,56,95,124,186,220,336,364,512,584,775,816,1129,1140,
%T A363604 1526,1600,1992,2024,2720,2620,3290,3400,4176,4060,5280,4960,6231,
%U A363604 6208,7362,7216,9195,8436,10280,10248,12270,11480,14432,13244,16192,15884,18240
%N A363604 Expansion of Sum_{k>0} x^(2*k)/(1-x^k)^4.
%H A363604 Seiichi Manyama, <a href="/A363604/b363604.txt">Table of n, a(n) for n = 1..10000</a>
%F A363604 a(n) = (sigma_3(n) - sigma(n))/6 = A092348(n)/6.
%F A363604 G.f.: Sum_{k>0} binomial(k+1,3) * x^k/(1 - x^k).
%F A363604 From _Amiram Eldar_, Dec 30 2024: (Start)
%F A363604 Dirichlet g.f.: zeta(s) * (zeta(s-3) - zeta(s-1)) / 6.
%F A363604 Sum_{k=1..n} a(k) ~ (zeta(4)/24) * n^4. (End)
%t A363604 a[n_] := (DivisorSigma[3, n] - DivisorSigma[1, n])/6; Array[a, 50] (* _Amiram Eldar_, Jul 25 2023 *)
%o A363604 (PARI) my(N=50, x='x+O('x^N)); concat(0, Vec(sum(k=1, N, x^(2*k)/(1-x^k)^4)))
%o A363604 (PARI) a(n) = my(f = factor(n)); (sigma(f, 3) - sigma(f))/6; \\ _Amiram Eldar_, Dec 30 2024
%Y A363604 Cf. A000292, A032741, A065608, A069153, A363605, A363606.
%Y A363604 Cf. A059358, A363607, A363611.
%Y A363604 Cf. A000203, A001158, A013662, A092348.
%K A363604 nonn,easy
%O A363604 1,3
%A A363604 _Seiichi Manyama_, Jun 11 2023