A012731 arctan(arctanh(x)*arctan(x))=2/2!*x^2-32/6!*x^6+283392/10!*x^10...

2, -32, 283392, 1121740800, 157951397068800, 14184297129466920960, 5248874425245870210416640, 2544005109030684773416383283200

Offset

0,1

Links

Table of n, a(n) for n=0..7.

Mathematica

With[{nn=30}, Take[CoefficientList[Series[ArcTan[ArcTanh[x]*ArcTan[x]], {x, 0, nn}], x] Range[0, nn]!, {3, -1, 4}]] (* Ray Chandler, Nov 28 2016 *)

Crossrefs

Sequence in context: A128146 A185995 A012604 * A073402 A304145 A305485

Adjacent sequences: A012728 A012729 A012730 * A012732 A012733 A012734

Keyword

sign

Author

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

Status

approved