OFFSET
0,4
FORMULA
a(n) ~ n! * (2*cos(3*n*Pi/4)*(1 - exp(4) - 2*exp(2)*sin(2)) + 2*(1 - exp(4) + 2*exp(2)*sin(2))*sin(3*n*Pi/4)) / ((1 + exp(4) + 2*exp(2)*cos(2)) * 2^(1+n/2)). - Vaclav Kotesovec, Jan 24 2015
MATHEMATICA
Tanh[ x ]/Cosh[ Log[ 1+x ] ]
CoefficientList[Series[(2*(1 + x)*Tanh[x])/(1 + (1 + x)^2), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 24 2015 *)
CROSSREFS
KEYWORD
sign,easy
AUTHOR
EXTENSIONS
Extended with signs by Olivier Gérard, Mar 15 1997
STATUS
approved