A191574 - OEIS

%I #5 Dec 18 2015 18:17:40

%S 2,8,64,1024,31744,1935544,233799896,55948528920,26536519769600,

%T 24832233133823360,45900199968106888384,167513350972291906490904,

%U 1207375485963640678858065184

%N Number of n X n symmetric binary matrices with each 1 adjacent to no more than 6 knight-move neighboring 1s

%e Some solutions for n=6

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

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

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

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

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

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

%K nonn

%O 1,1

%A _R. H. Hardin_ Jun 06 2011