OFFSET
2,1
LINKS
Seiichi Manyama, Table of n, a(n) for n = 2..1000
FORMULA
For n >= 2, a(n) = Sum_{k = 1..n-1} C(n-1,k-1)*C(n,k+1)*C(n+1,k), where C(n,k) = binomial(n,k).
a(n) = (1/(n+2)) * ((7*n^2-7*n-2)*a(n-1)/(n-2) + 8*n*a(n-2)) for n > 3. - Seiichi Manyama, Jan 09 2021
MATHEMATICA
Table[Sum[Binomial[n-1, k-1]Binomial[n, k+1]Binomial[n+1, k], {k, n-1}], {n, 2, 20}] (* Harvey P. Dale, May 08 2016 *)
PROG
(PARI) a(n) = sum(k=1, n-1, binomial(n-1, k-1)*binomial(n, k+1)*binomial(n+1, k)); \\ Michel Marcus, Jan 09 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Peter Bala, Oct 12 2011
STATUS
approved