OFFSET
0,1
FORMULA
a(n) ~ (2*n)! / (arctan((1-sqrt(2) + sqrt(2*sqrt(2)-1)) / (sqrt(2)-1 + sqrt(2*sqrt(2)-1))))^(2*n+1). - Vaclav Kotesovec, Feb 05 2015
MATHEMATICA
With[{nn=30}, Take[CoefficientList[Series[ArcTanh[Tan[x]+Sin[x]], {x, 0, nn}], x]Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Jun 26 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
Definition clarified by Harvey P. Dale, Jun 26 2012
STATUS
approved