A012098 sech(arcsin(arctan(x)))=1-1/2!*x^2+9/4!*x^4-249/6!*x^6+13297/8!*x^8...

1, -1, 9, -249, 13297, -1175761, 154625721, -28328562313, 6890453792609, -2147692998841633, 834418870682339561, -395288520944694504345, 224249503561141591847505, -150078278389547160573482225

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sech[ArcSin[ArcTan[x]]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Oct 26 2019 *)

Crossrefs

Sequence in context: A300757 A289551 A012202 * A012072 A007408 A066989

Adjacent sequences: A012095 A012096 A012097 * A012099 A012100 A012101

Keyword

sign

Author

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

Status

approved