OFFSET
1,4
COMMENTS
Row 4 of A187606.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..50
FORMULA
Empirical: a(n) = 55*n^2 - 380*n + 640 for n>5.
Conjectures from Colin Barker, Apr 25 2018: (Start)
G.f.: x^4*(28 + 60*x - 8*x^2 + 59*x^3 - 29*x^4) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>8.
(End)
EXAMPLE
Some solutions for 5 X 5:
..0..0..0..0..0....0..0..0..1..0....0..0..0..0..4....0..0..2..0..0
..0..0..0..0..0....0..0..0..0..0....0..0..3..0..0....1..0..0..4..0
..0..0..2..0..0....0..0..2..0..0....0..0..0..2..0....0..3..0..0..0
..1..0..0..4..0....0..0..0..4..0....0..0..0..0..1....0..0..0..0..0
..0..0..0..0..3....0..0..0..0..3....0..0..0..0..0....0..0..0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 11 2011
STATUS
approved