%I #6 Mar 31 2012 12:36:19
%S 48,576,11520,403200,25401600,2743372800,526727577600,176980466073600,
%T 104064514051276800,107810836557122764800,195461046678063572582400,
%U 622543433669632478674944000,3480017794213245555792936960000
%N Number of (n+2)X(n+2) symmetric binary matrices without the pattern 1 0 1 antidiagonally
%H R. H. Hardin, <a href="/A190601/b190601.txt">Table of n, a(n) for n = 1..49</a>
%e Some solutions for 4X4
%e ..0..1..0..1....1..0..0..1....0..1..0..1....1..1..1..0....1..1..0..0
%e ..1..0..1..1....0..0..0..0....1..1..1..1....1..1..0..0....1..0..1..0
%e ..0..1..1..1....0..0..0..0....0..1..1..1....1..0..1..0....0..1..1..0
%e ..1..1..1..1....1..0..0..0....1..1..1..0....0..0..0..1....0..0..0..1
%K nonn
%O 1,1
%A _R. H. Hardin_ May 13 2011