OFFSET
0,3
FORMULA
a(n) ~ (n-1)! / (2 * r^n), where r = 0.60134676772581981740108057557172913327... is the root of the equation exp(r)-cos(r) = 1. - Vaclav Kotesovec, Feb 05 2015
MATHEMATICA
CoefficientList[Series[ArcTanh[E^x - Cos[x]], {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Feb 05 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
Offset changed to 0 and added a(0)=0 by Vaclav Kotesovec, Feb 05 2015
STATUS
approved