A012850 cosh(sec(x)*arctanh(x))=1+1/2!*x^2+21/4!*x^4+765/6!*x^6+46473/8!*x^8...

1, 1, 21, 765, 46473, 4371225, 594635613, 110691178325, 27018807872657, 8370279766396593, 3208469378545620005, 1491108362472114151469, 826269720877603294674201, 538334287550086657620232905

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Cosh[Sec[x]ArcTanh[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Mar 24 2018 *)

Crossrefs

Sequence in context: A201069 A143002 A062755 * A012645 A220069 A028469

Adjacent sequences: A012847 A012848 A012849 * A012851 A012852 A012853

Keyword

nonn

Author

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

Status

approved