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 A261637 #4 Aug 28 2015 03:16:23
%S A261637 1,4,6,4,5,16,24,20,26,48,56,60,98,132,130,168,253,288,324,448,539,
%T A261637 588,780,1000,1086,1304,1690,1916,2205,2812,3274,3648,4507,5396,6018,
%U A261637 7200,8674,9680,11250,13616,15425,17532,20962,23988,26960,31868,36836,41164
%N A261637 Expansion of Product_{k>=0} (1+x^(3*k+1))^4.
%F A261637 a(n) ~ exp(2*Pi*sqrt(n)/3) / (2^(1/3) * sqrt(3) * n^(3/4)).
%t A261637 nmax=50; CoefficientList[Series[Product[(1+x^(3*k+1))^4, {k, 0, nmax}], {x, 0, nmax}], x]
%Y A261637 Cf. A261612, A261615, A261638.
%K A261637 nonn
%O A261637 0,2
%A A261637 _Vaclav Kotesovec_, Aug 27 2015