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 A293020 #6 Oct 06 2017 18:20:10
%S A293020 1,1,4,33,384,5705,103392,2213225,54648832,1529006769,47806489600,
%T A293020 1651929898641,62514008358912,2571311967708601,114219516618117120,
%U A293020 5449390043986849305,277913379747357786112,15087434965491213149153,868698417435317196816384,52875073161897308106963585
%N A293020 a(n) = n! * [x^n] exp(n*tan(x)).
%F A293020 a(n) ~ c * d^n * n^n / exp(n), where d = 3.2897906634948022290195938576166779380... and c = 0.7144692216716261155107169918... - _Vaclav Kotesovec_, Oct 06 2017
%t A293020 Table[n! SeriesCoefficient[Exp[n Tan[x]], {x, 0, n}], {n, 0, 19}]
%Y A293020 Cf. A006229, A133941.
%K A293020 nonn
%O A293020 0,3
%A A293020 _Ilya Gutkovskiy_, Sep 28 2017