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%I
%S 1,4,84,4432,432144,67336512,15330202432,4799825862912,
%T 1978228668612864,1038257514383795200,676117122084133770240,
%U 534973800492211106598912,505535479689176978173726720
%N arctanh(arcsin(sinh(x)))=x+4/3!*x^3+84/5!*x^5+4432/7!*x^7+432144/9!*x^9...
%F a(n) ~ (2*n)! / (arcsinh(sin(1)))^(2*n+1). - _Vaclav Kotesovec_, Feb 05 2015
%t nn = 20; Table[(CoefficientList[Series[ArcTanh[ArcSin[Sinh[x]]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* _Vaclav Kotesovec_, Feb 05 2015 *)
%K nonn
%O 0,2
%A Patrick Demichel (patrick.demichel(AT)hp.com)
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