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 A261386 #16 Apr 14 2019 07:51:24
%S A261386 1,4,16,56,176,520,1456,3896,10048,25100,60960,144440,334752,760456,
%T A261386 1696464,3722224,8043040,17135624,36031104,74840568,153680928,
%U A261386 312198160,627828272,1250540024,2468443296,4830809868,9377190336,18061370288,34531009760,65552873736
%N A261386 Expansion of Product_{k>=1} ((1+x^k)/(1-x^k))^(2*k).
%C A261386 Convolution of A161870 and A026011.
%H A261386 Seiichi Manyama, <a href="/A261386/b261386.txt">Table of n, a(n) for n = 0..10000</a>
%H A261386 Vaclav Kotesovec, <a href="http://arxiv.org/abs/1509.08708">A method of finding the asymptotics of q-series based on the convolution of generating functions</a>, arXiv:1509.08708 [math.CO], Sep 30 2015, p. 19.
%F A261386 a(n) ~ exp(1/6 + 3/2*(7*Zeta(3))^(1/3) * n^(2/3)) * (7*Zeta(3))^(2/9) / (A^2 * 2^(2/3) * n^(13/18) * sqrt(3*Pi)), where Zeta(3) = A002117 and A = A074962 is the Glaisher-Kinkelin constant.
%F A261386 G.f.: exp(Sum_{k>=1} (sigma_2(2*k) - sigma_2(k))*x^k/k). - _Ilya Gutkovskiy_, Apr 14 2019
%t A261386 nmax = 40; CoefficientList[Series[Product[(1+x^k)^(2*k) / (1-x^k)^(2*k), {k, 1, nmax}], {x, 0, nmax}], x]
%Y A261386 Cf. A015128, A026011, A156616, A161870, A216406, A261384, A261389.
%K A261386 nonn
%O A261386 0,2
%A A261386 _Vaclav Kotesovec_, Aug 17 2015