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 A326863 #3 Jul 27 2019 08:14:57
%S A326863 1,2,4,12,48,288,2016,14112,112896,1096704,12063744,135894528,
%T A326863 1630734336,22157549568,331366920192,5107664314368,82057393668096,
%U A326863 1436821272133632,27168078863794176,528845513033908224,10627947138360803328,228216184936879620096,5219125284175176794112
%N A326863 E.g.f.: Product_{k>=1} (1 + x^(4*k-3)/(4*k-3)) / (1 - x^(4*k-3)/(4*k-3)).
%F A326863 a(n) ~ 4 * exp(-gamma/2) * sqrt(n) * n! / Pi, where gamma is the Euler-Mascheroni constant A001620.
%t A326863 nmax = 30; CoefficientList[Series[Product[(1+x^(4*k-3)/(4*k-3))/(1-x^(4*k-3)/(4*k-3)), {k, 1, Floor[nmax/4]+1}], {x, 0, nmax}], x] * Range[0, nmax]!
%Y A326863 Cf. A326856, A326780.
%Y A326863 Cf. A305199, A326859, A326861, A326862.
%K A326863 nonn
%O A326863 0,2
%A A326863 _Vaclav Kotesovec_, Jul 27 2019