OFFSET
0,3
FORMULA
a(n) ~ 2 * cos(sqrt(Pi/2)) * (2*n)! / (sqrt(2*Pi) * sin(sqrt(Pi/2))^(2*n+1)). - Vaclav Kotesovec, Feb 08 2015
MATHEMATICA
nn = 20; Table[(CoefficientList[Series[Sec[ArcSin[x]^2], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Feb 08 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved