login
A211085
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
0
0, 1, 12, 504, 54552, 18314238, 18001425828, 52877461613730, 461270181887973636, 11975672062199372507844, 924700036496758370728369296
OFFSET
1,3
EXAMPLE
Some solutions for n=4
..3..3..1..1....2..2..3..0....2..2..1..1....2..2..3..0....3..3..0..0
..3..3..0..2....2..2..3..0....2..0..0..1....2..3..3..0....3..1..1..1
..1..0..0..2....3..3..3..1....1..0..2..2....3..3..3..0....0..1..1..0
..1..2..2..2....0..0..1..1....1..1..2..2....0..0..0..0....0..1..0..0
CROSSREFS
Sequence in context: A279302 A227052 A176731 * A197600 A197984 A197771
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 31 2012
STATUS
approved