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 A334854 #4 May 13 2020 19:00:14
%S A334854 1,2,7,32,149,240,-12725,-378880,-8550135,-178474240,-3550577425,
%T A334854 -65428992000,-985800819875,-4641229465600,548638404441075,
%U A334854 36708748623872000,1716785996161588625,69798035394846720000,2571598453132219756375,84313566554397999104000
%N A334854 E.g.f. A(x) satisfies: A(x) = arctan(x * exp(A(x))).
%F A334854 E.g.f.: series reversion of tan(x) / exp(x).
%t A334854 nmax = 20; CoefficientList[InverseSeries[Series[Tan[x]/Exp[x], {x, 0, nmax}], x], x] Range[0, nmax]! // Rest
%Y A334854 Cf. A227464, A227466.
%K A334854 sign
%O A334854 1,2
%A A334854 _Ilya Gutkovskiy_, May 13 2020