A191477 - OEIS

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

%S 2,5,15,92,716,8595,156804,4204649,170016558,10240395108,922770471915,

%T 124331209274267,25029189338772296,7533759271342997075,

%U 3389438730483714015640,2279436096066483952197622

%N Number of n X n symmetric binary matrices with each 1 adjacent to no more than 1 king-move neighboring 1

%H R. H. Hardin, <a href="/A191477/b191477.txt">Table of n, a(n) for n = 1..24</a>

%e Some solutions for n=4

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

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

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

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

%K nonn

%O 1,1

%A _R. H. Hardin_ Jun 03 2011