%I
%S 1,4,40,1216,123776,44030464,56185705472,261929007759360,
%T 4520504755804536832
%N Half the number of n X n binary matrices with row sum i equal to column sum i, i in 1..n.
%K nonn
%O 1,2
%A _R. H. Hardin_, Jun 13 2008
