A012737 sech(arctanh(x)*arctan(x))=1-12/4!*x^4-3248/8!*x^8-25240512/12!*x^12...

1, -12, -3248, -25240512, -722745554688, -61363036297915392, -12105663188188359045120, -4791193110632356981925068800

Offset

0,2

Links

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

Mathematica

With[{nn=34}, Take[CoefficientList[Series[Sech[ArcTanh[x]*ArcTan[x]], {x, 0, nn}], x] Range[0, nn-2]!, {1, -1, 4}]] (* Ray Chandler, Nov 28 2016 *)

Crossrefs

Sequence in context: A268048 A271516 A012603 * A370298 A077299 A077749

Adjacent sequences: A012734 A012735 A012736 * A012738 A012739 A012740

Keyword

sign

Author

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

Status

approved