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 A012394 #9 Feb 08 2015 06:00:59
%S A012394 1,0,12,480,32592,3644160,601225152,136477985280,40777726478592,
%T A012394 15519265846026240,7330634507726810112,4208431377781384765440,
%U A012394 2886028889205733569318912,2330210584650322816604897280
%N A012394 sec(tan(x)*tan(x))=1+12/4!*x^4+480/6!*x^6+32592/8!*x^8...
%H A012394 Vaclav Kotesovec, <a href="/A012394/b012394.txt">Table of n, a(n) for n = 0..200</a>
%H A012394 Vaclav Kotesovec, <a href="/A012394/a012394.jpg">Graph - abs(e.g.f.) in the complex plane</a>
%F A012394 a(n) ~ 2^(3/2) * (2*n)! / ((2+Pi) * sqrt(Pi) * (arctan(sqrt(Pi/2)))^(2*n+1)). - _Vaclav Kotesovec_, Feb 08 2015
%t A012394 nn = 20; Table[(CoefficientList[Series[Sec[Tan[x]^2], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* _Vaclav Kotesovec_, Feb 08 2015 *)
%K A012394 nonn
%O A012394 0,3
%A A012394 Patrick Demichel (patrick.demichel(AT)hp.com)