A012732 cos(arctanh(x)*arctan(x)) = 1-12/4!*x^4-9968/8!*x^8-77575872/12!*x^12...

1, -12, -9968, -77575872, -2494079278848, -227607911866125312, -47454799045677121597440, -19613396255307422099013550080, -14538029942147907114791552602275840

Offset

0,2

Links

Table of n, a(n) for n=0..8.

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Cos[ArcTanh[x]*ArcTan[x]], {x, 0, nn}], x] Range[0, nn-2]!, {1, -1, 4}]] (* Ray Chandler, Nov 28 2016 *)

Crossrefs

Sequence in context: A012532 A343699 A346717 * A001322 A159411 A074983

Adjacent sequences: A012729 A012730 A012731 * A012733 A012734 A012735

Keyword

sign

Author

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

Status

approved