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 A012466 #10 Jan 13 2013 06:14:00
%S A012466 1,0,12,-480,37968,-4773120,878319552,-222512349696,74262725323008,
%T A012466 -31578556041732096,16666719859336276992,-10690478515516973015040,
%U A012466 8190555666463900906475520,-7387658525325188387856384000
%N A012466 E.g.f. sec(arctan(x)^2) (even powers only).
%e A012466 sec(arctan(x)^2) = =1+12/4!*x^4-480/6!*x^6+37968/8!*x^8+-...
%t A012466 With[{nn=30},Take[CoefficientList[Series[Sec[ArcTan[x]^2],{x,0,nn}],x]Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Jan 12 2013 *)
%K A012466 sign
%O A012466 0,3
%A A012466 Patrick Demichel (patrick.demichel(AT)hp.com)