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A009391 Expansion of log(1 + tanh(x))/cos(x). 2
0, 1, -1, 3, -4, 25, -61, 427, -1184, 12465, -49201, 555731, -2361844, 35135945, -191422141, 2990414715, -17147588384, 329655706465, -2289437638081, 45692713833379, -329955144475204, 7777794952988025, -65643617893832221 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

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

FORMULA

a(n) ~ n! * 2^(n+1) * (Pi + (1+(-1)^n) * log(2/(1+exp(Pi)))) / Pi^(n+1). - Vaclav Kotesovec, Jan 24 2015

MATHEMATICA

Log[ 1+Tanh[ x ] ]/Cos[ x ]

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

CROSSREFS

a(2n+1) = A009843(n), |a(2n)| = A009391(2n).

Sequence in context: A338425 A304210 A245244 * A212696 A192346 A335739

Adjacent sequences:  A009388 A009389 A009390 * A009392 A009393 A009394

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 September 27 08:22 EDT 2021. Contains 347689 sequences. (Running on oeis4.)