OFFSET
0,4
MAPLE
a[0]:=1: a[1]:=1: a[2]:=1: for n from 3 to 20 do a[n]:=(n-1)*a[n-1]+(n-2)*a[n-2]+(n-3)*a[n-3] od: seq(a[n], n=0..20);
MATHEMATICA
a[0] = 1; a[1] = 1; a[2] = 1; a[n_] := a[n] = (n - 1)*a[n - 1] + (n - 2)*a[n - 2] + (n - 3)*a[n - 3] Table[a[n], {n, 0, 50}]
RecurrenceTable[{a[0]==a[1]==a[2]==1, a[n]==(n-1)a[n-1]+(n-2)a[n-2]+ (n-3)a[n-3]}, a, {n, 50}] (* Harvey P. Dale, Jul 10 2012 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Roger L. Bagula, Sep 21 2006
EXTENSIONS
Edited by N. J. A. Sloane, Oct 08 2006
Offset changed to 0 by Georg Fischer, Jun 18 2021
STATUS
approved