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 A009253 #13 Jan 27 2014 09:12:48
%S A009253 1,1,1,6,21,112,717,4592,38857,318208,3158329,32169984,363525789,
%T A009253 4399544320,56250039237,779244812288,11210469917713,173483433263104,
%U A009253 2783865475754737,47421793222656000,840008000833503141
%N A009253 Expansion of exp(tan(x)/cos(x)).
%t A009253 With[{nn=30},CoefficientList[Series[Exp[Tan[x]/Cos[x]],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Sep 30 2012 *)
%K A009253 nonn,easy
%O A009253 0,4
%A A009253 _R. H. Hardin_
%E A009253 Extended and signs tested Mar 15 1997 by _Olivier Gérard_.