A012769 - OEIS

%I #8 Feb 07 2015 03:46:29

%S 1,3,45,1071,69177,3986939,609782693,60159520487,18315680711153,

%T 2425226987446387,1432393396034388637,194035475753231168543,

%U 248503763037617443112745,18849742079674987910368107

%N tan(cosh(x)*arctan(x))=x+3/3!*x^3+45/5!*x^5+1071/7!*x^7+69177/9!*x^9...

%C Note that a(15) is negative. - _Vaclav Kotesovec_, Feb 07 2015

%H Vaclav Kotesovec, <a href="/A012769/b012769.txt">Table of n, a(n) for n = 0..200</a>

%t nn = 20; Table[(CoefficientList[Series[Tan[ArcTan[x]*Cosh[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* _Vaclav Kotesovec_, Feb 07 2015 *)

%K sign

%O 0,2

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