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 A012395 #6 Feb 27 2013 16:06:03
%S A012395 1,0,-12,-480,-15792,387840,232592448,44951262720,4538494871808,
%T A012395 -1173690989322240,-1020600368000166912,-406075179314308669440,
%U A012395 -50036577406600515366912,87776293107173235762462720
%N A012395 sech(tan(x)*tan(x))=1-12/4!*x^4-480/6!*x^6-15792/8!*x^8...
%t A012395 With[{nn=30},Take[CoefficientList[Series[Sech[Tan[x]^2],{x,0,nn}],x] Range[ 0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Feb 27 2013 *)
%K A012395 sign
%O A012395 0,3
%A A012395 Patrick Demichel (patrick.demichel(AT)hp.com)