a(n) = (n+1)*(n+2)/2 * Sum_{k=0..floor(n/2)} n!/(n-2*k)!.
A114633
a(n) = (n+1)*(n+2)/2 * Sum_{k=0..floor(n/2)} n!/(n-2*k)!.
Terms
- a(0) =1a(1) =3a(2) =18a(3) =70a(4) =555a(5) =2961a(6) =31108a(7) =213228a(8) =2799765a(9) =23455135a(10) =369569046a(11) =3659001138a(12) =67261566463a(13) =768390239085
External references
- oeis: A114633