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A012177 tan(tan(arctanh(x)))=x+6/3!*x^3+176/5!*x^5+11792/7!*x^7... 1

%I

%S 1,6,176,11792,1399808,258010112,68048472064,24288413734912,

%T 11265869660880896,6584336654436794368,4732528038730841194496,

%U 4101916559962554300891136,4218542156655644369974460416

%N tan(tan(arctanh(x)))=x+6/3!*x^3+176/5!*x^5+11792/7!*x^7...

%H Vaclav Kotesovec, <a href="/A012177/b012177.txt">Table of n, a(n) for n = 0..195</a>

%F a(n) = 8*(2*n+1)! / ((4+Pi^2) * cosh(arctan(Pi/2))^2 * tanh(arctan(Pi/2))^(2*n+2)). - _Vaclav Kotesovec_, Feb 06 2015

%t nn = 20; Table[(CoefficientList[Series[Tan[Tan[ArcTanh[x]]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* _Vaclav Kotesovec_, Feb 06 2015 *)

%K nonn

%O 0,2

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

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Last modified October 16 05:38 EDT 2019. Contains 328044 sequences. (Running on oeis4.)