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 A009197 #13 Jul 02 2015 12:46:32
%S A009197 1,1,0,-3,-6,35,135,-476,-6300,14349,298515,254056,-26673042,
%T A009197 -26975169,1931306377,16803854768,-336040323112,-1435742838615,
%U A009197 20743481564487,843925791375728,-11354618863953550,-37784454009996005
%N A009197 Expansion of exp(log(1+x)/cosh(x)).
%H A009197 Vaclav Kotesovec, <a href="/A009197/b009197.txt">Table of n, a(n) for n = 0..200</a>
%F A009197 a(n) ~ n! * (-1)^n / (GAMMA(-1/cosh(1)) * n^(1+1/cosh(1))). - _Vaclav Kotesovec_, Jul 02 2015
%t A009197 CoefficientList[Series[Exp[Log[1+x]/Cosh[x]], {x, 0, 20}], x] * Range[0, 20]! (* _Vaclav Kotesovec_, Jul 02 2015 *)
%K A009197 sign,easy
%O A009197 0,4
%A A009197 _R. H. Hardin_
%E A009197 Extended with signs by _Olivier Gérard_, Mar 15 1997