OFFSET
0,2
COMMENTS
Since a(18) are all terms positive. - Vaclav Kotesovec, Feb 08 2015
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..200
FORMULA
a(n) ~ sqrt(Pi) * (2*n)! / (n^(3/2) * (1 + cosh(Pi^2/2))). - Vaclav Kotesovec, Feb 08 2015
MATHEMATICA
nn = 20; Table[(CoefficientList[Series[Tanh[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
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
a(0)=0 prepended by Vaclav Kotesovec, Feb 08 2015
STATUS
approved