A012097 sec(arcsin(arctan(x)))=1+1/2!*x^2+1/4!*x^4+49/6!*x^6-447/8!*x^8...

1, 1, 1, 49, -447, 78561, -5655231, 1014069393, -187639949439, 51144433721793, -16631972691697791, 6837287119716744945, -3357388632038371909695, 1969419543279480607781025

Offset

0,4

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sec[ArcSin[ArcTan[x]]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Nov 28 2019 *)

Crossrefs

Sequence in context: A063132 A250081 A250082 * A218594 A263706 A263707

Adjacent sequences: A012094 A012095 A012096 * A012098 A012099 A012100

Keyword

sign

Author

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

Status

approved