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 A293191 #12 Nov 21 2020 21:37:39
%S A293191 1,1,4,30,320,4420,74880,1502200,34816000,915267600,26907545600,
%T A293191 874679634400,31150846771200,1206169954600000,50449154129920000,
%U A293191 2266730426366640000,108883850653859840000,5568313898902866592000,302047359993635143680000,17321727685903810436800000
%N A293191 a(n) = n! * [x^n] exp(n*arcsin(x)).
%F A293191 a(n) ~ 2^((n-1)/2) * exp(Pi*n/4 - n) * n^n. - _Vaclav Kotesovec_, Oct 02 2017
%F A293191 a(0) = a(1) = 1; a(n) = 2 * Sum_{k=1..n-1} binomial(n,k) * a(k) * a(n-k-1). - _Ilya Gutkovskiy_, Nov 21 2020
%t A293191 Table[n! SeriesCoefficient[Exp[n ArcSin[x]], {x, 0, n}], {n, 0, 19}]
%Y A293191 Cf. A002866, A006228, A166741.
%K A293191 nonn
%O A293191 0,3
%A A293191 _Ilya Gutkovskiy_, Oct 02 2017