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A012347 tanh(arcsin(x)*arcsin(x))=2/2!*x^2+8/4!*x^4-112/6!*x^6-8832/8!*x^8... 1
0, 2, 8, -112, -8832, -269568, 18508800, 4584990720, 373223424000, -57291983093760, -29502109561651200, -4280300758758850560, 1571738277174218588160, 1306880625182819525591040 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Since a(18) are all terms positive. - Vaclav Kotesovec, Feb 08 2015

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..200

FORMULA

a(n) ~ sqrt(Pi) * (2*n)! / (n^(3/2) * (1 + cosh(Pi^2/2))). - Vaclav Kotesovec, Feb 08 2015

MATHEMATICA

nn = 20; Table[(CoefficientList[Series[Tanh[ArcSin[x]^2], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Feb 08 2015 *)

CROSSREFS

Sequence in context: A211938 A005787 A012343 * A263249 A297631 A099292

Adjacent sequences:  A012344 A012345 A012346 * A012348 A012349 A012350

KEYWORD

sign

AUTHOR

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

EXTENSIONS

a(0)=0 prepended by Vaclav Kotesovec, Feb 08 2015

STATUS

approved

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Last modified November 12 16:45 EST 2019. Contains 329058 sequences. (Running on oeis4.)