A012464 arctanh(arctan(x)*arctan(x))=2/2!*x^2-16/4!*x^4+608/6!*x^6-43776/8!*x^8...

0, 2, -16, 608, -43776, 5490432, -1043742720, 281302333440, -101944270848000, 47833801306275840, -28212954337286553600, 20432760600063600230400, -17826780360146975037849600, 18441699370235590444905922560

Offset

0,2

Links

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

Formula

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

Mathematica

nn = 20; Table[(CoefficientList[Series[ArcTanh[ArcTan[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: A060279 A369674 A012757 * A277036 A289202 A279324

Adjacent sequences: A012461 A012462 A012463 * A012465 A012466 A012467

Keyword

sign

Author

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

Extensions

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

Status

approved