%I
%S 0,1,6,348,28140,8126604,5661794106,11445238420311,62094025253816664,
%T 936614735379619968930,38691771579576015771775929
%N 1/4 the number of n X n 0..3 symmetric matrices with every element equal to one or two horizontal and vertical neighbors
%e Some solutions for n=4
%e ..2..2..0..3....0..0..3..3....1..1..0..0....2..2..2..3....0..0..0..0
%e ..2..0..0..3....0..0..0..3....1..2..2..3....2..3..3..3....0..1..1..2
%e ..0..0..1..1....3..0..0..0....0..2..2..3....2..3..1..1....0..1..1..2
%e ..3..3..1..1....3..3..0..0....0..3..3..3....3..3..1..1....0..2..2..2
%K nonn
%O 1,3
%A _R. H. Hardin_ Mar 31 2012
