%I
%S 0,6,540,123480,57405600,47488518000,63760174077600,
%T 129947848862832000,382114148130658944000,1557871091922736150560000,
%U 8528480929388117171073600000,61063236793210618551364940160000
%N a(n) is the number of (0,1) matrices A=(a_{ij}) of size n X (3n) such each row has exactly three 1's and each column has exactly one 1 and with the restriction that no 1 stands on the diagonal from a_{11} to a_{22}.
%F a(n)= sum_{k=0..n} (1)^k (3nk)!/(6^{nk}*2^k) * binomial(n,k).
%o (PARI) a(n)= sum(k=0, n, (1)^k *(3*nk)! /(6^(nk)*2^k) * binomial(n,k)) \\ _Michel Marcus_, Jul 25 2013
%K nonn
%O 1,2
%A _Shanzhen Gao_, Feb 24 2010
