OFFSET
0,2
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..218
FORMULA
a(n) ~ c * (-1)^n * (2*n)! / (sqrt(n) * r^(2*n)), where r = 0.867011256808704179615963011549544766868066027225... is the root of the equation arctan(r)*cosh(r) = 1, c = 0.741862954403555... . - Vaclav Kotesovec, Feb 04 2015
MATHEMATICA
nn = 20; Table[(CoefficientList[Series[ArcSinh[ArcTanh[x]*Cos[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Feb 04 2015 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved