%I #5 Dec 18 2015 18:18:07
%S 1,5,34,504,12656,595218,51772998,8410205156,2530816613400,
%T 1415636007880172,1467795266440304666,2820089447984802286032
%N 1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors
%e Some solutions for n=4
%e ..2..0..1..0....2..2..2..1....2..0..2..0....2..1..0..0....0..1..2..0
%e ..0..2..0..2....2..0..2..2....0..2..0..2....1..2..0..0....1..2..0..2
%e ..1..0..1..1....2..2..0..2....2..0..2..1....0..0..0..1....2..0..1..0
%e ..0..2..1..1....1..2..2..2....0..2..1..2....0..0..1..0....0..2..0..1
%K nonn
%O 1,2
%A _R. H. Hardin_ Mar 30 2012
|