OFFSET
1,4
COMMENTS
Row 3 of A187172.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..50
FORMULA
Empirical: a(n) = 12*n^2 - 64*n + 80 for n>3.
G.f.: 4*x^4*(4 - x)*(1 + x) / (1 - x)^3 (conjectured). - Colin Barker, Apr 22 2018
EXAMPLE
Some solutions for 4 X 4:
..0..0..2..0....0..0..1..0....0..0..0..0....0..0..0..0....0..0..1..0
..3..0..0..0....0..0..0..0....3..0..0..0....0..0..2..0....2..0..0..0
..0..0..0..1....0..0..0..2....0..0..0..1....3..0..0..0....0..0..0..0
..0..0..0..0....0..3..0..0....0..2..0..0....0..0..0..1....0..3..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 06 2011
STATUS
approved