OFFSET
0,2
LINKS
Vaclav Kotesovec, Graph - abs(e.g.f.) in the complex plane
FORMULA
a(n) ~ 2 * (cos(r))^2 * (2*n+1)! / ((1-(cos(r))^3) * r^(2*n+2)), where r = 1.19018423208957072372902875764508033454996553596790725617361... is the root of the equation tan(r)-sin(r) = Pi/2. Also r = arcsin(t), where t = 0.928437423168555149184... is the root of the equation 4*t^4 + 4*Pi*t^3 + Pi^2*t^2 - 4*Pi*t - Pi^2 = 0. - Vaclav Kotesovec, Feb 06 2015
MATHEMATICA
nn = 20; Table[(CoefficientList[Series[-Tan[Sin[x] - Tan[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Feb 06 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
a(0)=0 prepended by Vaclav Kotesovec, Feb 06 2015
Definition modified by Vaclav Kotesovec, Feb 06 2015
STATUS
approved