%I #7 Feb 05 2015 12:04:47

%S 1,3,41,1467,100625,11103155,1795927225,400540116971,117802787966241,

%T 44174901566136419,20571101104110689353,11646565567973048707867,

%U 7878351005250269762378801,6275481526065593121954975251

%N arctanh(tan(sin(x)))=x+3/3!*x^3+41/5!*x^5+1467/7!*x^7+100625/9!*x^9...

%F a(n) ~ (2*n)! / (arcsin(Pi/4))^(2*n+1). - _Vaclav Kotesovec_, Feb 05 2015

%t nn = 20; Table[(CoefficientList[Series[ArcTanh[Tan[Sin[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)