A012016 - OEIS

%I #10 Oct 09 2018 15:29:21

%S 1,3,41,1299,74609,6787811,898506649,163241051315,39007280136801,

%T 11866656488375747,4479287777805494665,2054673461380880189779,

%U 1125793481954983195433681,726247496033154181534638755

%N arctanh(sin(tan(x)))=x+3/3!*x^3+41/5!*x^5+1299/7!*x^7+74609/9!*x^9...

%F a(n) ~ 2 * (2*n)! / (arctan(Pi/2))^(2*n+1). - _Vaclav Kotesovec_, Oct 24 2013

%t Table[n!*SeriesCoefficient[ArcTanh[Sin[Tan[x]]],{x,0,n}] ,{n,1,40,2}] (* _Vaclav Kotesovec_, Oct 24 2013 *)

%t With[{nn=30},Take[CoefficientList[Series[ArcTanh[Sin[Tan[x]]],{x,0,nn}],x] Range[0,nn-1]!,{2,-1,2}]] (* _Harvey P. Dale_, Oct 09 2018 *)

%Y Bisection of A009329.

%K nonn

%O 0,2

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