|
|
A211086
|
|
1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one, two or three horizontal and vertical neighbors
|
|
1
|
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
EXAMPLE
|
Some solutions for n=4
..0..2..0..2....0..0..2..3....0..0..0..3....0..2..1..2....0..2..3..0
..2..1..1..0....0..1..2..1....0..2..0..3....2..0..0..2....2..2..3..2
..0..1..2..3....2..2..0..3....0..0..2..2....1..0..1..3....3..3..1..3
..2..0..3..0....3..1..3..0....3..3..2..0....2..2..3..0....0..2..3..2
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|