A102075 Expansion of sec(arctanh(x)).

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

Offset: 0

Author

Ralf Stephan, Dec 31 2004

Keywords

• nonn

Examples

			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! -...
		

Programs

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 *)