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-arctanh(log(cos(x))) = 1/2!*x^2+2/4!*x^4+46/6!*x^6+1112/8!*x^8...
0

%I #8 Oct 25 2013 10:04:15

%S 1,2,46,1112,63376,4635872,523749136,76049858432,14634264866176,

%T 3496967323112192,1032537134569578496,366067157640456292352,

%U 154146217678162805226496,75874517780279404503590912

%N -arctanh(log(cos(x))) = 1/2!*x^2+2/4!*x^4+46/6!*x^6+1112/8!*x^8...

%t Table[n!*SeriesCoefficient[-ArcTanh[Log[Cos[x]]],{x,0,n}],{n,2,40,2}] (* _Vaclav Kotesovec_, Oct 25 2013 *)

%K nonn

%O 0,2

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