A012754 - OEIS

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A012754

exp(arctanh(x)*tanh(x)) = 1+2/2!*x^2+12/4!*x^4+280/6!*x^6+13328/8!*x^8...

1, 2, 12, 280, 13328, 1016608, 120249536, 19735743872, 4349101334784, 1233253332705792, 437938810884459520, 190333673674118699008, 99369086035110941036544, 61369835997419856216006656

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

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

FORMULA

a(n) ~ 2 * (2*n-1)! * (4*n)^c / GAMMA(c), where c = tanh(1)/2 = (exp(2)-1)/(exp(2)+1)/2. - Vaclav Kotesovec, Oct 24 2013

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Exp[ArcTanh[x]Tanh[x]], {x, 0, nn}], x]Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Apr 21 2012 *)

CROSSREFS

Sequence in context: A214005 A014982 A012444 * A083568 A003121 A211937

Adjacent sequences: A012751 A012752 A012753 * A012755 A012756 A012757

KEYWORD

nonn

AUTHOR

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

STATUS

approved