%I #6 Dec 18 2015 18:17:40
%S 1,0,2,16,244,6938,371342,37280140,7016898676,2476338996046,
%T 1638683680332022,2033288154472125378,4730646433644468299754,
%U 20637618504497727985203276,168817037972490215464239418020
%N Half the number of n X n symmetric binary matrices with no element both equal to all its immediate N and W neighbors if they exist and unequal to all its immediate E and S neighbors if they exist
%H R. H. Hardin, <a href="/A192325/b192325.txt">Table of n, a(n) for n = 1..21</a>
%e Some solutions for 4X4 with a(1,1)=0
%e ..0..0..0..1....0..0..0..0....0..0..0..0....0..0..1..0....0..0..1..0
%e ..0..1..0..1....0..1..1..0....0..1..0..0....0..0..0..0....0..0..0..1
%e ..0..0..1..0....0..1..0..1....0..0..1..0....1..0..1..0....1..0..0..0
%e ..1..1..0..1....0..0..1..0....0..0..0..1....0..0..0..1....0..1..0..1
%K nonn
%O 1,3
%A _R. H. Hardin_ Jun 28 2011