%I
%S 1,5,166,35207,30211455,99371076165,1250065064815292,
%T 60143467055359131310,11066941546543240934864887,
%U 7788436930452056534815427874703,20963150916521213172749181596782816735
%N Number of n X n 0..3 symmetric matrices with every element equal to zero, one or two horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order
%H R. H. Hardin, <a href="/A210923/b210923.txt">Table of n, a(n) for n = 1..12</a>
%e Some solutions for n=4
%e ..0..0..2..3....0..1..1..1....0..0..1..3....0..1..0..3....0..1..3..0
%e ..0..1..0..2....1..0..2..3....0..0..1..2....1..2..2..0....1..2..2..0
%e ..2..0..2..3....1..2..1..2....1..1..2..3....0..2..1..3....3..2..0..1
%e ..3..2..3..2....1..3..2..3....3..2..3..0....3..0..3..0....0..0..1..0
%K nonn
%O 1,2
%A _R. H. Hardin_ Mar 29 2012
