OFFSET
1,2
COMMENTS
Row 4 of A187027.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..31
FORMULA
Empirical: a(n) = 3504*n^2 - 18540*n + 24444 for n>5.
Conjectures from Colin Barker, Apr 20 2018: (Start)
G.f.: 4*x^2*(6 + 318*x + 774*x^2 + 602*x^3 + 117*x^4 - 9*x^5 - 56*x^6) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>8.
(End)
EXAMPLE
Some solutions for 4 X 4:
..0..0..0..0....2..0..3..4....0..0..0..4....0..0..0..0....0..2..0..0
..0..0..0..1....0..1..0..0....1..2..3..0....2..3..0..0....4..1..3..0
..0..0..3..4....0..0..0..0....0..0..0..0....1..0..0..0....0..0..0..0
..0..0..0..2....0..0..0..0....0..0..0..0....0..4..0..0....0..0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 02 2011
STATUS
approved