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