A012620 sec(arcsinh(x)*tan(x))=1+12/4!*x^4+120/6!*x^6+15120/8!*x^8...

1, 0, 12, 120, 15120, 640320, 143136576, 14091272832, 5105629251840, 906008454739968, 490783256100396032, 136461255865204086784, 104233836908816608661504, 41544908070600747941806080

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sec[ArcSinh[x]Tan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jun 16 2025 *)

Crossrefs

Sequence in context: A301898 A012441 A012373 * A012564 A012442 A262204

Adjacent sequences: A012617 A012618 A012619 * A012621 A012622 A012623

Keyword

nonn

Author

Patrick Demichel

Status

approved