OFFSET
0,1
FORMULA
a(n) ~ (2*n+1)! / (arctan(sqrt((1+sqrt(5))/2)))^(2*n+2). - Vaclav Kotesovec, Oct 24 2013
MATHEMATICA
Table[n!*SeriesCoefficient[ArcTanh[Tan[x]*Sin[x]], {x, 0, n}], {n, 2, 40, 2}] (* Vaclav Kotesovec, Oct 24 2013 *)
With[{nn=30}, Take[CoefficientList[Series[ArcTanh[Tan[x]Sin[x]], {x, 0, nn}], x] Range[0, nn]!, {3, -1, 2}]] (* Harvey P. Dale, Feb 15 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved