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%I #3 Mar 31 2012 12:35:07
%S 1,2,5,20,139,1777,42295,1888140,158903233,25355226287,7707419775769
%N Half the number of symmetric n X n binary matrices having equal row sums.
%K nonn
%O 1,2
%A _R. H. Hardin_, Jul 28 2008