%I #7 Mar 31 2012 12:36:19
%S 56,728,17472,768768,62270208,9278260992,2542243511808,
%T 1281290729951232,1187756506664792064,2025124843863470469120,
%U 6350791510355843391160320,36631365431732504680212725760,388622155865250142152376807587840
%N Number of (n+2)X(n+2) symmetric binary matrices without the pattern 1 1 1 diagonally
%H R. H. Hardin, <a href="/A190419/b190419.txt">Table of n, a(n) for n = 1..62</a>
%e Some solutions for n=2
%e ..1..0..1..0....1..1..1..0....1..1..0..1....0..1..1..0....1..0..0..1
%e ..0..0..0..0....1..1..0..1....1..0..0..0....1..1..0..0....0..1..0..1
%e ..1..0..0..1....1..0..0..1....0..0..0..1....1..0..0..0....0..0..0..1
%e ..0..0..1..0....0..1..1..0....1..0..1..0....0..0..0..1....1..1..1..1
%K nonn
%O 1,1
%A _R. H. Hardin_ May 10 2011