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 A009443 #12 Jun 23 2015 22:06:16
%S A009443 0,1,-1,-1,6,-11,0,83,-784,6921,-34560,-60281,2821632,-29132611,
%T A009443 184690688,-208438245,-19939461120,427918448785,-5036475875328,
%U A009443 22588439158415,504121321717760,-15853957892902395,258254373528797184
%N A009443 Expansion of log(1+x/cosh(x)).
%t A009443 Log[ 1+x/Cosh[ x ] ]
%t A009443 CoefficientList[Series[Log[1 + x*Sech[x]], {x, 0, 20}], x] * Range[0, 20]! (* _Vaclav Kotesovec_, Jan 24 2015 *)
%K A009443 sign,easy
%O A009443 0,5
%A A009443 _R. H. Hardin_
%E A009443 Extended with signs by _Olivier Gérard_, Mar 15 1997