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A012551 arctanh(sinh(x)*tan(x))=2/2!*x^2+12/4!*x^4+382/6!*x^6+23352/8!*x^8... 0

%I

%S 2,12,382,23352,2464922,398069892,91079960662,28062488827632,

%T 11197997254599602,5618500857338248572,3461960315033768973742,

%U 2569953015248391982844712,2262189595338137069466955082

%N arctanh(sinh(x)*tan(x))=2/2!*x^2+12/4!*x^4+382/6!*x^6+23352/8!*x^8...

%F a(n) ~ (2*n+1)! / r^(2*n+2), where r = 0.825607669071161851569946... is the real root of the equation tan(r)*sinh(r)=1. - _Vaclav Kotesovec_, Oct 24 2013

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

%K nonn

%O 0,1

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

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Last modified September 29 09:23 EDT 2022. Contains 357088 sequences. (Running on oeis4.)