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A012618 arctanh(arcsinh(x)*tan(x))=2/2!*x^2+4/4!*x^4+350/6!*x^6+7208/8!*x^8... 0
0, 2, 4, 350, 7208, 1520218, 106485740, 38051376246, 6123846322896, 3217389043510578, 964215477538459732, 692917532440212444686, 338776184246581290006520, 318786053587029917056642186 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..13.

FORMULA

a(n) ~ (2*n-1)! / r^(2*n), where r = 0.89357177742189289... is the root of the equation r+sqrt(r^2+1) = exp(1/tan(r)). - Vaclav Kotesovec, Oct 31 2013

MATHEMATICA

Table[n!*SeriesCoefficient[ArcTanh[ArcSinh[x]*Tan[x]], {x, 0, n}], {n, 0, 40, 2}] (* Vaclav Kotesovec, Oct 31 2013 *)

CROSSREFS

Sequence in context: A009705 A012372 A012613 * A012557 A012562 A263959

Adjacent sequences: A012615 A012616 A012617 * A012619 A012620 A012621

KEYWORD

nonn

AUTHOR

Patrick Demichel (patrick.demichel(AT)hp.com)

EXTENSIONS

Prepended missing a(0)=0 from Vaclav Kotesovec, Oct 31 2013

STATUS

approved

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Last modified February 8 06:05 EST 2023. Contains 360134 sequences. (Running on oeis4.)