A012812 sec(sec(x)*arctan(x))=1+1/2!*x^2+9/4!*x^4+345/6!*x^6+14833/8!*x^8...

1, 1, 9, 345, 14833, 1493265, 158895033, 30935964969, 6150088646497, 1967749424641953, 629235472952720105, 300014790466799113849, 140704010339485622390865, 93651237671421167849769905

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sec[Sec[x]ArcTan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jan 06 2022 *)

Crossrefs

Sequence in context: A055601 A225328 A203745 * A266881 A119756 A222697

Adjacent sequences: A012809 A012810 A012811 * A012813 A012814 A012815

Keyword

nonn

Author

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

Status

approved