A012342 tan(arcsin(x)*arcsin(x))=2/2!*x^2+8/4!*x^4+368/6!*x^6+18048/8!*x^8...

0, 2, 8, 368, 18048, 1827072, 253363200, 50403563520, 13158813696000, 4414765984972800, 1841972633056051200, 936689336904269168640, 569861032837432328847360, 408713488929007199437455360

Offset

0,2

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..222

Vaclav Kotesovec, Graph - e.g.f. in the complex plane (absolute values)

Formula

a(n) ~ sqrt(2) * cos(sqrt(Pi/2)) * (2*n)! / (sqrt(Pi) * (sin(sqrt(Pi/2)))^(2*n+1)). - Vaclav Kotesovec, Feb 06 2015

Mathematica

nn = 20; Table[(CoefficientList[Series[Tan[ArcSin[x]^2], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Feb 06 2015 *)

Crossrefs

Sequence in context: A009489 A102597 A009836 * A012348 A219994 A014185

Adjacent sequences: A012339 A012340 A012341 * A012343 A012344 A012345

Keyword

nonn

Author

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

Extensions

a(0)=0 prepended by Vaclav Kotesovec, Feb 06 2015

Status

approved