A172562 Number of 3*n X n 0..1 arrays with row sums 2 and column sums 6.

0, 1, 1680, 32496156, 2604964362000, 666569141498660400, 452489654840076972518400, 712008996110160366168717566400, 2343976695927269878444049332219968000

Offset

1,3

References

Gao, Shanzhen, and Matheis, Kenneth, Closed formulas and integer sequences arising from the enumeration of (0,1)-matrices with row sum two and some constant column sums. In Proceedings of the Forty-First Southeastern International Conference on Combinatorics, Graph Theory and Computing. Congr. Numer. 202 (2010), 45-53.

Links

R. H. Hardin, Table of n, a(n) for n=1..33

Formula

2^(-3n)*Sum_{i=0..2n} ((-1)^i*(3n)!(2n)!(6n-2i)!/(i!(3n-i)!(2n-i)!6^(2n-i)))*g(n) = 4^(-2n)*((2n)!)^2*Sum_{i=0..2n} ((-2)^i*(4n-2i)!/(i!((2n-i)!)^2)). - Shanzhen Gao, Feb 16 2010

Crossrefs

Sequence in context: A343459 A282402 A156422 * A172568 A172673 A172768

Adjacent sequences: A172559 A172560 A172561 * A172563 A172564 A172565

Keyword

nonn

Author

R. H. Hardin, Feb 06 2010

Status

approved