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A102075 Expansion of sec(arctanh(x)). 5
1, 1, 13, 445, 28985, 3061625, 476598725, 102580436725, 29164947696625, 10583881430448625, 4773158983014768125, 2618414864448579438125, 1716782830141547577475625, 1325775140076807694645515625 (list; graph; refs; listen; history; text; internal format)
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: A260851 A260852 A012832 * A218586 A251601 A338177

Adjacent sequences:  A102072 A102073 A102074 * A102076 A102077 A102078

KEYWORD

nonn

AUTHOR

Ralf Stephan, Dec 31 2004

STATUS

approved

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Last modified August 3 00:25 EDT 2021. Contains 346429 sequences. (Running on oeis4.)