%I
%S 0,1,12,504,54552,18314238,18001425828,52877461613730,
%T 461270181887973636,11975672062199372507844,
%U 924700036496758370728369296
%N 1/4 the number of n X n 0..3 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors
%e Some solutions for n=4
%e ..3..3..1..1....2..2..3..0....2..2..1..1....2..2..3..0....3..3..0..0
%e ..3..3..0..2....2..2..3..0....2..0..0..1....2..3..3..0....3..1..1..1
%e ..1..0..0..2....3..3..3..1....1..0..2..2....3..3..3..0....0..1..1..0
%e ..1..2..2..2....0..0..1..1....1..1..2..2....0..0..0..0....0..1..0..0
%K nonn
%O 1,3
%A _R. H. Hardin_ Mar 31 2012
