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%I #7 Feb 08 2015 05:53:12
%S 0,2,16,392,21376,2117792,333550336,76433892992,23981418704896,
%T 9862199971860992,5144452992189485056,3317894031273853601792,
%U 2591931617534673513250816,2411532576645611695219515392
%N arcsin(tan(x)*tan(x))=2/2!*x^2+16/4!*x^4+392/6!*x^6+21376/8!*x^8...
%F a(n) ~ 2^(4*n-1) * (2*n)! / (n^(3/2) * Pi^(2*n)). - _Vaclav Kotesovec_, Feb 08 2015
%t nn = 20; Table[(CoefficientList[Series[ArcSin[Tan[x]^2], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* _Vaclav Kotesovec_, Feb 08 2015 *)
%K nonn
%O 0,2
%A Patrick Demichel (patrick.demichel(AT)hp.com)
%E a(0)=0 prepended by _Vaclav Kotesovec_, Feb 08 2015