A192676 Floor-Sqrt transform of derangement numbers (A000166).

1, 0, 1, 1, 3, 6, 16, 43, 121, 365, 1155, 3832, 13274, 47862, 179084, 693589, 2774358, 11438972, 48531450, 211543687, 946052129, 4335355493, 20334619731, 97521410321, 477755388567, 2388776942837, 12180420245150, 63291320166423, 334906186618646, 1803525009870353

Offset: 0

Author

Emanuele Munarini, Jul 07 2011

Keywords

• nonn

Crossrefs

Cf. A000166.

Programs

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]

Formula

a(n) = floor(sqrt(derangements(n))).