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A009443 Expansion of log(1+x/cosh(x)). 1
0, 1, -1, -1, 6, -11, 0, 83, -784, 6921, -34560, -60281, 2821632, -29132611, 184690688, -208438245, -19939461120, 427918448785, -5036475875328, 22588439158415, 504121321717760, -15853957892902395, 258254373528797184 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

LINKS

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

MATHEMATICA

Log[ 1+x/Cosh[ x ] ]

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

CROSSREFS

Sequence in context: A115677 A284738 A100129 * A258054 A106540 A212208

Adjacent sequences:  A009440 A009441 A009442 * A009444 A009445 A009446

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 February 16 21:59 EST 2019. Contains 320200 sequences. (Running on oeis4.)