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A009323 Expansion of log(1+log(1+x)/cosh(x)). 0
0, 1, -2, 4, -17, 113, -829, 6921, -68018, 766909, -9668901, 134950693, -2070353196, 34628733267, -626969184451, 12218295424331, -255041910240464, 5677409949583369, -134260064803417113, 3361378755164561417 (list; graph; refs; listen; history; text; internal format)
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: A212581 A305786 A009319 * 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

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Last modified January 29 10:34 EST 2020. Contains 331337 sequences. (Running on oeis4.)