A191222 - OEIS

%I #9 Dec 18 2015 18:17:39

%S 1,3,5,17,107,598,5688,77906,1352347,34249359,1204670396,58155968015,

%T 3946610726739,371524667930965,48587161215494423,8859996760746649440,

%U 2245679398171585663077,791847513412090215745935

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

%H R. H. Hardin, <a href="/A191222/b191222.txt">Table of n, a(n) for n = 1..24</a>

%e Some solutions for n=4

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_ May 27 2011