%I #3 Mar 31 2012 12:35:07
%S 1,2,3,9,21,113,469,4085,28379,421721,4946881,123415785,2438547133,
%T 102642272877,3418605422546,242398759656743,13604569959521965,
%U 1625856487869820237,153782502309772183952,30970307573051859177121,4936590429632104565792997,1675450994355334964940357075
%N Number of n X n binary matrices, symmetric about both diagonal and antidiagonal, with no more than 2 ones in any 2 X 2 subblock.
%K nonn
%O 0,2
%A _R. H. Hardin_, Aug 10 2008