A191224 - OEIS

%I #7 Dec 18 2015 18:17:39

%S 1,2,3,4,10,29,74,267,1270,6853,46338,452697,5888876,103743236,

%T 2568916974,83100685126,3548166614885,196909507948313,

%U 14058252177537760

%N Number of n X n symmetric binary matrices with each 1 adjacent to exactly 3 king-move neighboring 1s

%e All solutions for n=4

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_ May 27 2011