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%I #12 Jan 17 2018 10:27:17
%S 0,1,1680,32496156,2604964362000,666569141498660400,
%T 452489654840076972518400,712008996110160366168717566400,
%U 2343976695927269878444049332219968000
%N Number of 3*n X n 0..1 arrays with row sums 2 and column sums 6.
%D 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.
%H R. H. Hardin, <a href="/A172562/b172562.txt">Table of n, a(n) for n=1..33</a>
%F 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
%K nonn
%O 1,3
%A _R. H. Hardin_, Feb 06 2010
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