

A172562


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


1




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 FortyFirst Southeastern International Conference on Combinatorics, Graph Theory and Computing. Congr. Numer. 202 (2010), 4553.


LINKS

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


FORMULA

2^{3n}\sum_{i=0}^{2n}\frac{(1)^{i}(3n)!(2n)!(6n2i)!}{% %i!(3ni)!(2ni)!6^{2ni}}$ %$g(n)=4^{2n}((2n)!)^{2}\sum_{i=0}^{2n}\frac{(2)^{i}(4n2i)!}{% %i!((2ni)!)^{2}} [From Shanzhen Gao, Feb 16 2010]


CROSSREFS

Sequence in context: A234439 A060095 A156422 * A172568 A172673 A172768
Adjacent sequences: A172559 A172560 A172561 * A172563 A172564 A172565


KEYWORD

nonn


AUTHOR

R. H. Hardin Feb 06 2010


STATUS

approved



