A012041 - OEIS

%I #10 Feb 04 2015 07:30:41

%S 1,-4,76,-3312,255952,-30728512,5281229760,-1228900532992,

%T 371761489090816,-141763213277045760,66504626862819552256,

%U -37635004127910391803904,25277676503178610861756416

%N tanh(sin(arcsinh(x)))=x-4/3!*x^3+76/5!*x^5-3312/7!*x^7+255952/9!*x^9...

%H Vaclav Kotesovec, <a href="/A012041/b012041.txt">Table of n, a(n) for n = 0..220</a>

%F a(n) ~ c * (-1)^n * (2*n)! * n / r^(2*n), where r = sin(arcsinh(Pi/2)) = 0.9436207924237..., c = 0.79859796313... . - _Vaclav Kotesovec_, Feb 04 2015

%t nn = 20; Table[(CoefficientList[Series[Tanh[Sin[ArcSinh[x]]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* _Vaclav Kotesovec_, Feb 03 2015 *)

%K sign

%O 0,2

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