OFFSET
1,3
COMMENTS
Row 3 of A187606.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..50
FORMULA
Empirical: a(n) = 16*n^2 - 80*n + 100 for n>3.
Conjectures from Colin Barker, Apr 25 2018: (Start)
G.f.: x^3*(9 + 9*x + 19*x^2 - 5*x^3) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>6.
(End)
EXAMPLE
Some solutions for 5 X 5:
..0..0..0..0..0....0..0..0..0..0....0..0..0..1..0....0..0..0..3..0
..0..0..3..0..0....0..0..0..0..0....0..0..0..0..0....0..0..0..0..2
..0..0..0..2..0....0..0..1..0..0....0..0..2..0..0....0..0..1..0..0
..0..0..0..0..1....3..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..0..0..0..3....0..0..0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 11 2011
STATUS
approved