A012168 sec(tan(arcsinh(x)))=1+1/2!*x^2+9/4!*x^4+201/6!*x^6+7921/8!*x^8...

1, 1, 9, 201, 7921, 524081, 48396345, 6493605561, 1082018699105, 246352273609441, 64161902428428265, 22422522791742857001, 8300517886009938036049, 4196071192877342442444561

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sec[Tan[ArcSinh[x]]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Apr 24 2017 *)

Crossrefs

Sequence in context: A093708 A052145 A012061 * A012133 A012038 A012108

Adjacent sequences: A012165 A012166 A012167 * A012169 A012170 A012171

Keyword

nonn

Author

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

Status

approved