A211085 - OEIS

%I #5 Dec 18 2015 18:18:07

%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