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 A009239 #12 Jun 04 2018 18:41:19
%S A009239 1,1,1,4,13,68,373,2528,19097,160400,1522409,15384128,174263717,
%T A009239 2066458176,27072485469,369136141824,5477315064625,84457146691840,
%U A009239 1398343023229393,24053254928131072,439386703590146365
%N A009239 Expansion of e.g.f.: exp(tan(sinh(x))).
%t A009239 With[{nn=20},CoefficientList[Series[Exp[Tan[Sinh[x]]],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Jun 04 2018 *)
%K A009239 nonn,easy
%O A009239 0,4
%A A009239 _R. H. Hardin_
%E A009239 Extended and signs tested Mar 15 1997 by _Olivier Gérard_.
%E A009239 Definition clarified and prior Mathematica program replaced by _Harvey P. Dale_, Jun 04 2018