OFFSET
1,2
EXAMPLE
Some solutions for n=4
..1..1..2..1....2..0..1..0....1..2..0..1....2..0..0..2....1..2..0..1
..1..1..2..1....0..2..2..2....2..2..1..2....0..2..0..0....2..1..0..2
..2..2..0..1....1..2..0..1....0..1..1..2....0..0..2..2....0..0..1..1
..1..1..1..1....0..2..1..1....1..2..2..2....2..0..2..2....1..2..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 30 2012
STATUS
approved