A190341 - OEIS

%I #5 Mar 31 2012 12:36:19

%S 3,9,40,273,2727,41520,944307,32403123,1667310336,129124175985,

%T 15018894671481,2626862719652352,690390044069042835,

%U 272767004386769371833,161965593156881121867648

%N Number of (n+1)X(n+1) symmetric binary matrices without the pattern 1 1 diagonally or antidiagonally

%H R. H. Hardin, <a href="/A190341/b190341.txt">Table of n, a(n) for n = 1..25</a>

%e Some solutions for 3X3

%e ..0..0..0....1..0..0....0..0..0....0..0..1....0..0..1....1..0..1....1..0..1

%e ..0..0..0....0..0..0....0..1..0....0..0..0....0..0..0....0..0..0....0..0..0

%e ..0..0..0....0..0..0....0..0..0....1..0..1....1..0..0....1..0..1....1..0..0

%K nonn

%O 1,1

%A _R. H. Hardin_ May 09 2011