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A012098 sech(arcsin(arctan(x)))=1-1/2!*x^2+9/4!*x^4-249/6!*x^6+13297/8!*x^8... 0
1, -1, 9, -249, 13297, -1175761, 154625721, -28328562313, 6890453792609, -2147692998841633, 834418870682339561, -395288520944694504345, 224249503561141591847505, -150078278389547160573482225 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 2 18:27 EDT 2022. Contains 355029 sequences. (Running on oeis4.)