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tan(arctanh(x)-log(x+1)) = 1/2!*x^2 + 6/4!*x^4 + 150/6!*x^6 + 7560/8!*x^8...
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%I #9 Feb 06 2015 11:25:58

%S 0,1,6,150,7560,642600,82328400,14799985200,3550699152000,

%T 1095489931536000,422416533258720000,199001229578030880000,

%U 112442434205652270720000,75042084306026165328000000

%N tan(arctanh(x)-log(x+1)) = 1/2!*x^2 + 6/4!*x^4 + 150/6!*x^6 + 7560/8!*x^8...

%F a(n) ~ 2 * (2*n)! * exp(Pi*n) / (exp(Pi)-1)^(n+1). - _Vaclav Kotesovec_, Feb 06 2015

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

%K nonn

%O 0,3

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

%E a(0)=0 prepended by _Vaclav Kotesovec_, Feb 06 2015

%E Definition modified by _Vaclav Kotesovec_, Feb 06 2015