A009842 Expansion of tanh(x)/cosh(log(1+x)).

0, 1, 0, -5, 12, 6, -120, 442, -2352, 13192, 53280, -1665432, 12223200, -6629648, -706340544, 9387463888, -95898673920, 563447710848, 8308014488064, -283290718941056, 3505513923832320, -9173243369732864, -499029405102412800

Offset

0,4

Links

Table of n, a(n) for n=0..22.

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

Sequence in context: A335102 A342069 A046610 * A169729 A070368 A066326

Adjacent sequences: A009839 A009840 A009841 * A009843 A009844 A009845

Keyword

sign,easy

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved