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 A009272 #21 Aug 25 2025 04:28:57
%S A009272 1,2,12,232,7952,405152,31111872,3115956352,414147567872,
%T A009272 68413355397632,13936708915940352,3412444856961083392,
%U A009272 987956358173680013312,334650367409781717573632,130572314003924554412900352,58337032599905770133366013952
%N A009272 Expansion of e.g.f. exp(tanh(x)*tan(x)), even powers only.
%t A009272 With[{nn=30},Take[CoefficientList[Series[Exp[Tanh[x]Tan[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Feb 26 2012 *)
%K A009272 nonn,changed
%O A009272 0,2
%A A009272 _R. H. Hardin_
%E A009272 Extended and signs tested by _Olivier Gérard_, Mar 15 1997
%E A009272 More terms from _Harvey P. Dale_, Feb 26 2012