OFFSET
0,2
FORMULA
a(n)=sum{k=0..floor(n/2), (2(n-k))!/(2k)!}
MATHEMATICA
Table[Sum[(2(n-k))!/(2k)!, {k, 0, Floor[n/2]}], {n, 0, 20}] (* Harvey P. Dale, Aug 26 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, May 25 2006
STATUS
approved