OFFSET
0,5
FORMULA
a(n) = floor(sqrt(derangements(n))).
MATHEMATICA
FSFromExpSeries[f_, x_, n_] := Map[Floor[Sqrt[#]]&, CoefficientList[Series[f, {x, 0, n}], x]Table[k!, {k, 0, n}]]
FSFromExpSeries[Exp[-x]/(1-x), x, 100]
CROSSREFS
KEYWORD
nonn
AUTHOR
Emanuele Munarini, Jul 07 2011
STATUS
approved