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 A009166 #12 Jan 24 2015 08:09:37
%S A009166 1,0,12,240,9296,558720,47965632,5537249536,823842474240,
%T A009166 153119256219648,34710583399132160,9416311849673895936,
%U A009166 3009741915237844832256,1118809461121375449088000
%N A009166 Expansion of cosh(tan(x)*x).
%F A009166 a(n) ~ (2*n)! * 2^(2*n-7/4) * exp(2*sqrt(2*n)-1/2) / (n^(3/4) * Pi^(2*n+1/2)). - _Vaclav Kotesovec_, Jan 24 2015
%t A009166 Cosh[ Tan[ x ]*x ] (* Even Part *)
%t A009166 nn = 20; Table[(CoefficientList[Series[Cosh[x*Tan[x]], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* _Vaclav Kotesovec_, Jan 24 2015 *)
%K A009166 nonn
%O A009166 0,3
%A A009166 _R. H. Hardin_
%E A009166 Extended and signs tested Mar 15 1997 by _Olivier Gérard_.