A012852 sech(sec(x)*arctanh(x))=1-1/2!*x^2-15/4!*x^4-225/6!*x^6+3297/8!*x^8...

1, -1, -15, -225, 3297, 973695, 99434577, 3364479391, -1767300967487, -640573924497921, -102867079807004495, 22939113754550703391, 27513402069157221548193, 11830594343212717024871295

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sech[Sec[x]ArcTanh[x]], {x, 0, nn}], x] Range[ 0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Aug 07 2022 *)

Crossrefs

Sequence in context: A224191 A224349 A224008 * A171289 A262336 A189906

Adjacent sequences: A012849 A012850 A012851 * A012853 A012854 A012855

Keyword

sign

Author

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

Status

approved