OFFSET
1,2
COMMENTS
Column 4 of A215959.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..20
EXAMPLE
Some solutions for n=4
..0..x..1..x....0..x..1..x....0..x..1..x....0..x..1..x....0..x..1..x
..x..2..x..3....x..1..x..0....x..1..x..2....x..2..x..3....x..2..x..3
..4..x..0..x....2..x..3..x....3..x..4..x....2..x..4..x....2..x..0..x
..x..1..x..2....x..4..x..2....x..5..x..1....x..3..x..5....x..0..x..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 28 2012
STATUS
approved