A012164 - OEIS

%I #9 Oct 30 2013 17:07:15

%S 1,2,16,216,6400,125696,18156672,-930421504,394852151296,

%T -97538559528960,37824762737852416,-16526000392804139008,

%U 8864261701679059992576,-5567468507542446595047424

%N sinh(tan(arcsinh(x))) = x+2/3!*x^3+16/5!*x^5+216/7!*x^7+6400/9!*x^9...

%F a(n) ~ (-1)^n * 2^(2*n+2) * n^(2*n) * cos(tanh(Pi/2)) / ((cosh(Pi)+1) * exp(2*n)). - _Vaclav Kotesovec_, Oct 30 2013

%t Table[n!*SeriesCoefficient[Sinh[Tan[ArcSinh[x]]],{x,0,n}],{n,1,40,2}] (* _Vaclav Kotesovec_, Oct 30 2013 *)

%K sign

%O 0,2

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