A012180 tanh(tan(arctanh(x)))=x+2/3!*x^3+16/5!*x^5+48/7!*x^7-29696/9!*x^9...

1, 2, 16, 48, -29696, -6049792, -1262426112, -308569372672, -89297625350144, -30123113337716736, -11520007513318621184, -4775431672418431664128, -1952929261585732032528384, -545214673336986589066166272

Offset

0,2

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Tanh[Tan[ArcTanh[x]]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Sep 06 2023 *)

Crossrefs

Sequence in context: A223219 A063721 A232209 * A058376 A295906 A120948

Adjacent sequences: A012177 A012178 A012179 * A012181 A012182 A012183

Keyword

sign

Author

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

Status

approved