A009402 Expansion of log(1+tanh(x)/exp(x)).

0, 1, -3, 9, -42, 285, -2358, 23079, -264792, 3479625, -51399978, 843354699, -15223184892, 299785177965, -6395410234398, 146929245609519, -3616700960240592, 94961188049020305, -2649161419533345618

Offset

0,3

Links

Table of n, a(n) for n=0..18.

Formula

a(n) ~ (n-1)! * (-1)^(n+1) * 3^n / (log((7 + (199 - 3*sqrt(33))^(1/3) + (199 + 3*sqrt(33))^(1/3))/3))^n. - Vaclav Kotesovec, Jan 23 2015

Mathematica

Log[ 1+Tanh[ x ]/Exp[ x ] ]
CoefficientList[Series[Log[1 + Tanh[x]/E^x], {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 23 2015 *)

Crossrefs

Sequence in context: A018965 A357703 A105804 * A009584 A013562 A081681

Adjacent sequences: A009399 A009400 A009401 * A009403 A009404 A009405

Keyword

sign,easy

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved