A102075 Expansion of sec(arctanh(x)).

1, 1, 13, 445, 28985, 3061625, 476598725, 102580436725, 29164947696625, 10583881430448625, 4773158983014768125, 2618414864448579438125, 1716782830141547577475625, 1325775140076807694645515625

Offset

0,3

Links

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

Example

sec(arctanh(x)) = 1 + x^2/2 + 13x^4/4! + 445x^6/6! + 28985x^8/8! +...
sech(arctan(x)) = 1 - x^2/2 + 13x^4/4! - 445x^6/6! + 28985x^8/8! -...

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sec[ArcTanh[x]], {x, 0, nn}], x] Range[ 0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Nov 05 2020 *)

Crossrefs

Sequence in context: A260852 A372812 A012832 * A218586 A251601 A338177

Adjacent sequences: A102072 A102073 A102074 * A102076 A102077 A102078

Keyword

nonn

Author

Ralf Stephan, Dec 31 2004

Status

approved