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 A009255 #13 May 05 2019 14:04:20
%S A009255 1,1,-1,0,9,-28,65,294,-2751,21496,-69343,143154,4340193,-44055100,
%T A009255 549236753,-3053333154,25428876417,103583035888,-1719503726527,
%U A009255 62167764668394,-580794950152287,11376539928963260,-67379231311376719
%N A009255 Expansion of exp(tan(x)/exp(x)).
%t A009255 With[{nn=30},CoefficientList[Series[Exp[Tan[x]/Exp[x]],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, May 05 2019 *)
%K A009255 sign,easy
%O A009255 0,5
%A A009255 _R. H. Hardin_
%E A009255 Extended with signs by _Olivier Gérard_, Mar 15 1997
%E A009255 Previous Mathematica program replaced by _Harvey P. Dale_, May 05 2019