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 A009431 #13 Jun 23 2015 21:44:02
%S A009431 0,1,-1,-1,0,49,-165,-393,-504,70785,-434385,-517265,-12647976,
%T A009431 654552625,-6276987717,18362076327,-636272644560,22683808563841,
%U A009431 -312594994151361,2817355930176479,-72112751626318640,2222078368780722865
%N A009431 Expansion of log(1+x)/cosh(sin(x)).
%F A009431 a(n) ~ (n-1)! * (-1)^(n+1) / cosh(sin(1)). - _Vaclav Kotesovec_, Jan 23 2015
%t A009431 Log[ 1+x ]/Cosh[ Sin[ x ] ]
%t A009431 CoefficientList[Series[Log[1 + x]*Sech[Sin[x]], {x, 0, 20}], x] * Range[0, 20]! (* _Vaclav Kotesovec_, Jan 23 2015 *)
%K A009431 sign,easy
%O A009431 0,6
%A A009431 _R. H. Hardin_
%E A009431 Extended with signs by _Olivier Gérard_, Mar 15 1997