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A009836 Expansion of tanh(x)*tan(tan(x)). 1

%I

%S 0,2,8,368,16512,1583104,199552000,36445579264,8620299812864,

%T 2621816292114432,987354046567284736,452732308336619290624,

%U 247917555997339251900416,159904531672039230122491904

%N Expansion of tanh(x)*tan(tan(x)).

%F a(n) ~ (2*n)! * 8 * tanh(arctan(Pi/2)) / ((4 + Pi^2) * arctan(Pi/2)^(2*n+1)). - _Vaclav Kotesovec_, Jan 24 2015

%t Tanh[ x ]*Tan[ Tan[ x ] ] (* Even Part *)

%t nn = 20; Table[(CoefficientList[Series[Tan[Tan[x]]*Tanh[x], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* _Vaclav Kotesovec_, Jan 24 2015 *)

%K nonn

%O 0,2

%A _R. H. Hardin_

%E Extended and signs tested Mar 15 1997 by _Olivier GĂ©rard_.

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Last modified October 4 21:22 EDT 2022. Contains 357240 sequences. (Running on oeis4.)