A012061 sec(sin(arctanh(x)))=1+1/2!*x^2+9/4!*x^4+201/6!*x^6+7921/8!*x^8...

1, 1, 9, 201, 7921, 447281, 28121145, 230243001, -940995291295, -539358796035359, -280768914546419735, -156059839698555664599, -96215805882840361663151, -66431831409927100446899439

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sec[Sin[ArcTanh[x]]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Sep 24 2021 *)

Crossrefs

Sequence in context: A197077 A093708 A052145 * A012168 A012133 A012038

Adjacent sequences: A012058 A012059 A012060 * A012062 A012063 A012064

Keyword

sign

Author

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

Status

approved