A012208 tanh(arctan(arctan(x)))=x-6/3!*x^3+184/5!*x^5-13136/7!*x^7...

1, -6, 184, -13136, 1679488, -335723264, 96492653568, -37665610561536, 19158060131778560, -12304193595906129920, 9734505561510299566080, -9299736312230986726768640, 10553185490408007072659537920

Offset

0,2

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Tanh[ArcTan[ArcTan[x]]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Nov 15 2014 *)

Crossrefs

Sequence in context: A041429 A089905 A222887 * A012181 A012224 A274272

Adjacent sequences: A012205 A012206 A012207 * A012209 A012210 A012211

Keyword

sign

Author

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

Extensions

Definition clarified by Harvey P. Dale, Nov 15 2014

Status

approved