OFFSET
0,5
FORMULA
a(n) ~ (n-1)! * (-1)^(n+1) * (4/Pi)^n / cosh(Pi/4). - Vaclav Kotesovec, Jan 23 2015
MATHEMATICA
Log[ 1+Tan[ x ] ]/Cosh[ x ]
CoefficientList[Series[Log[1 + Tan[x]]*Sech[x], {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 23 2015 *)
CROSSREFS
KEYWORD
sign,easy
AUTHOR
EXTENSIONS
Extended with signs by Olivier Gérard, Mar 15 1997
STATUS
approved