A012144 sec(arcsin(arctanh(x)))=1+1/2!*x^2+17/4!*x^4+769/6!*x^6+66849/8!*x^8...

1, 1, 17, 769, 66849, 9506241, 2007271089, 589807203777, 230194642564161, 115219444193968257, 71962921603647030609, 54865853223458268869505, 50151129904368572197783905, 54139213630083955379966633025

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sec[ArcSin[ArcTanh[x]]], {x, 0, nn}], x] Range[ 0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jun 22 2022 *)

Crossrefs

Sequence in context: A355495 A368492 A012221 * A265190 A308490 A374946

Adjacent sequences: A012141 A012142 A012143 * A012145 A012146 A012147

Keyword

nonn

Author

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

Status

approved