A009323 Expansion of log(1+log(1+x)/cosh(x)).

0, 1, -2, 4, -17, 113, -829, 6921, -68018, 766909, -9668901, 134950693, -2070353196, 34628733267, -626969184451, 12218295424331, -255041910240464, 5677409949583369, -134260064803417113, 3361378755164561417

Offset

0,3

Links

Table of n, a(n) for n=0..19.

Formula

a(n) ~ (n-1)! * (-1)^(n+1) / (1-exp(-r))^n, where r = 1.2699247771697243287665144498039831430030774... is the root of the equation 1 + exp(-2 + 2*exp(-r)) - 2*exp(exp(-r)-1)*r = 0. - Vaclav Kotesovec, Jan 24 2015

Mathematica

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

Crossrefs

Sequence in context: A305786 A009319 A347724 * A307125 A247260 A048872

Adjacent sequences: A009320 A009321 A009322 * A009324 A009325 A009326

Keyword

sign,easy

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved