OFFSET
1,2
COMMENTS
Row 4 of A187507
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..50
FORMULA
Empirical: a(n) = 21*n^2 - 68*n + 51 for n>2.
Empirical G.f.: x^2*(2+30*x+13*x^2-3*x^3)/(1-x)^3. [Colin Barker, Jan 22 2012]
EXAMPLE
Some solutions for 4X4
..0..0..0..0....0..0..0..0....0..4..2..0....0..4..0..0....0..0..0..0
..1..2..3..0....0..1..0..0....0..0..3..1....0..2..3..0....0..1..2..0
..0..0..4..0....0..2..3..0....0..0..0..0....0..0..1..0....0..0..3..4
..0..0..0..0....0..0..4..0....0..0..0..0....0..0..0..0....0..0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 10 2011
STATUS
approved