A012086 sech(arcsin(tan(x)))=1-1/2!*x^2-7/4!*x^4-121/6!*x^6-5167/8!*x^8...

1, -1, -7, -121, -5167, -487441, -78804727, -18558463561, -5919443326687, -2457116797560481, -1289150916753299047, -834798631079038210201, -654139310316332313889807, -610085118687493622960844721

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sech[ArcSin[Tan[x]]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Sep 17 2023 *)

Crossrefs

Sequence in context: A316730 A211103 A012103 * A074487 A192566 A322090

Adjacent sequences: A012083 A012084 A012085 * A012087 A012088 A012089

Keyword

sign

Author

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

Status

approved