%I
%S 1,2,1,7,4,49,21,648,245,16475,5184,801489,214175,74700792,16831269,
%T 13333992705,2539826928,4558747755857,733369598775,2985167883475040,
%U 405728550271273,3743977846899435969,429864175220405760
%N Number of n X n binary matrices, symmetric about the diagonal and under 90degree rotation, with no more than 3 ones in any 2 X 2 subblock.
%H R. H. Hardin, <a href="/A141512/b141512.txt">Table of n, a(n) for n = 0..30</a>
%K nonn
%O 0,2
%A _R. H. Hardin_, Aug 10 2008
