%I A139688
%S A139688 1,4,40,1216,123776,44030464,56185705472,261929007759360,
%T A139688 4520504755804536832
%N A139688 Half the number of n X n binary matrices with row sum i equal to column 
               sum i, i in 1..n.
%Y A139688 Sequence in context: A013108 A111846 A102922 this_sequence A072445 A000841 
               A059918
%Y A139688 Adjacent sequences: A139685 A139686 A139687 this_sequence A139689 A139690 
               A139691
%K A139688 nonn
%O A139688 1,2
%A A139688 Ron Hardin (rhhardin(AT)att.net), Jun 13 2008