A055219 T(2n+3,n), array T as in A055216.

1, 5, 21, 78, 274, 927, 3061, 9933, 31824, 100972, 317942, 995088, 3099105, 9612735, 29715525, 91595391, 281643480, 864189486, 2646805668, 8093543439, 24713953515, 75370741506, 229604257846, 698754428388, 2124616182139

Offset: 0

Author

Clark Kimberling, May 07 2000

Keywords

• nonn

Formula

Apparently a(n)=sum((-1)^j*binomial(n+3, j)*binomial(2n+3-3j, n+3), j=0..floor(n/3)). - Emeric Deutsch, Mar 13 2004