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 A293192 #9 Oct 02 2017 18:57:08
%S A293192 1,1,4,21,128,745,1440,-89075,-3031040,-76951215,-1784742400,
%T A293192 -39056351675,-785147904000,-12815410658375,-64977212518400,
%U A293192 8229576066616125,587339977981952000,29185361934747006625,1256364637107240960000,48860370609512175371125,1686271331087959982080000
%N A293192 a(n) = n! * [x^n] exp(n*arctan(x)).
%t A293192 Table[n! SeriesCoefficient[Exp[n ArcTan[x]], {x, 0, n}], {n, 0, 20}]
%t A293192 Table[n! SeriesCoefficient[Exp[n Sum[(-1)^k x^(2 k + 1)/(2 k + 1), {k, 0, Infinity}]], {x, 0, n}], {n, 0, 20}]
%Y A293192 Cf. A002019.
%K A293192 sign
%O A293192 0,3
%A A293192 _Ilya Gutkovskiy_, Oct 02 2017