A012121 sec(arcsin(arcsinh(x)))=1+1/2!*x^2+5/4!*x^4+109/6!*x^6+3177/8!*x^8...

1, 1, 5, 109, 3177, 227961, 15773229, 2521786149, 294715261521, 91106569198449, 14283819393505749, 8353531761471301725, 1366332291998753348025, 1671117489759750577634025, 171277162439935833445571325, 660477991317304143815464418325

Offset

0,3

Links

Table of n, a(n) for n=0..15.

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sec[ArcSin[ArcSinh[x]]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Oct 09 2017 *)

Crossrefs

Sequence in context: A195552 A318292 A012239 * A371882 A014180 A012122

Adjacent sequences: A012118 A012119 A012120 * A012122 A012123 A012124

Keyword

nonn

Author

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

Extensions

More terms from Harvey P. Dale, Oct 09 2017

Status

approved