A140988 - OEIS

%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