A012372 arctanh(tan(x)*sin(x))=2/2!*x^2+4/4!*x^4+302/6!*x^6+8104/8!*x^8...

2, 4, 302, 8104, 1189562, 113466604, 28069843622, 6004208983504, 2285772143562482, 867405503682334804, 478060568033873866142, 280896639757518649936504, 213833919524790465586194602

Offset

0,1

Links

Table of n, a(n) for n=0..12.

Formula

a(n) ~ (2*n+1)! / (arctan(sqrt((1+sqrt(5))/2)))^(2*n+2). - Vaclav Kotesovec, Oct 24 2013

Mathematica

Table[n!*SeriesCoefficient[ArcTanh[Tan[x]*Sin[x]], {x, 0, n}], {n, 2, 40, 2}] (* Vaclav Kotesovec, Oct 24 2013 *)
With[{nn=30}, Take[CoefficientList[Series[ArcTanh[Tan[x]Sin[x]], {x, 0, nn}], x] Range[0, nn]!, {3, -1, 2}]] (* Harvey P. Dale, Feb 15 2018 *)

Crossrefs

Sequence in context: A012434 A012368 A009705 * A012613 A012618 A012557

Adjacent sequences: A012369 A012370 A012371 * A012373 A012374 A012375

Keyword

nonn

Author

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

Status

approved