A009443 Expansion of log(1+x/cosh(x)).

0, 1, -1, -1, 6, -11, 0, 83, -784, 6921, -34560, -60281, 2821632, -29132611, 184690688, -208438245, -19939461120, 427918448785, -5036475875328, 22588439158415, 504121321717760, -15853957892902395, 258254373528797184

Offset: 0

Author

R. H. Hardin

Keywords

• sign
• easy

Programs

Mathematica

Log[ 1+x/Cosh[ x ] ]
CoefficientList[Series[Log[1 + x*Sech[x]], {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 24 2015 *)

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997