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 A235131 #9 Sep 23 2022 17:03:56
%S A235131 1,1,3,23,201,2401,33723,564983,10832721,235620481,5715989043,
%T A235131 153231400343,4495861836441,143343873560161,4934418832685163,
%U A235131 182409363179578103,7206898465033427361,303073359560984509441,13516205633151976330083,637174194752117499594263
%N A235131 E.g.f. 1/(1 - tan(2*x))^(1/2).
%C A235131 Generally, for e.g.f. 1/(1-tan(p*x))^(1/p) is a(n) ~ n! * 2^(2*n+1/p) * p^n / (Gamma(1/p) * Pi^(n+1/p) * n^(1-1/p)).
%F A235131 a(n) ~ n! * 2^(3*n+1/2) / (Pi^(n+1) * sqrt(n)).
%t A235131 CoefficientList[Series[1/(1 - Tan[2*x])^(1/2), {x, 0, 20}], x] * Range[0, 20]!
%Y A235131 Cf. A000828 (p=1), A235132 (p=3).
%K A235131 nonn,easy
%O A235131 0,3
%A A235131 _Vaclav Kotesovec_, Jan 03 2014