OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..50
FORMULA
Empirical: a(n) = 8*n^2 - 12*n for n>1.
Empirical g.f.: 4*x^2*(2+3*x-x^2)/(1-x)^3. - Colin Barker, Jan 22 2012
EXAMPLE
Some solutions for 4 X 4:
..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..2..0..1
..1..0..0..0....0..1..0..0....0..1..2..0....2..0..0..0....0..0..0..0
..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0
..2..0..0..0....0..2..0..0....0..0..0..0....1..0..0..0....0..0..0..0
MAPLE
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 08 2011
STATUS
approved