OFFSET
0,2
FORMULA
a(n) ~ (2*n)! * 2^(2*n+1) * exp((2*n+1)*Pi/4) / (exp(Pi/2)-1)^(2*n+1). - Vaclav Kotesovec, Oct 30 2013
MATHEMATICA
Table[n!*SeriesCoefficient[ArcTanh[Tan[ArcSinh[x]]], {x, 0, n}], {n, 1, 40, 2}] (* Vaclav Kotesovec, Oct 30 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved