A012156 - OEIS

A012156

arctanh(tan(sinh(x)))=x+5/3!*x^3+121/5!*x^5+7069/7!*x^7+763057/9!*x^9...

1, 5, 121, 7069, 763057, 132103157, 33527321257, 11731117858573, 5412661283979361, 3184128808387236581, 2326120405922560979929, 2066008261961436163683709, 2192446490036211173903631121

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..12.

FORMULA

a(n) ~ (2*n)! / (arcsinh(Pi/4))^(2*n+1). - Vaclav Kotesovec, Feb 05 2015

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[ArcTanh[Tan[Sinh[x]]], {x, 0, nn}], x]Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Mar 17 2012 *)

CROSSREFS

Sequence in context: A012077 A012046 A012151 * A368854 A290167 A193479

Adjacent sequences: A012153 A012154 A012155 * A012157 A012158 A012159

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

More terms from N. J. A. Sloane, Aug 27 2006

STATUS

approved