OFFSET
1,1
COMMENTS
Column 2 of A183433.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..171
FORMULA
Empirical: a(n) = 9*a(n-1) + a(n-2) - 9*a(n-3).
Conjectures from Colin Barker, Mar 29 2018: (Start)
G.f.: x*(4 - 9*x - 3*x^2) / ((1 - x)*(1 + x)*(1 - 9*x)).
a(n) = 9^n / 3 for n even.
a(n) = (6+2*9^n) / 6 for n odd.
(End)
EXAMPLE
Some solutions for 3 X 2:
..1..2....2..0....3..1....2..2....1..3....3..0....0..1....0..2....3..3....1..1
..1..2....3..0....3..0....2..2....2..2....2..0....3..1....1..3....3..0....0..1
..3..0....2..0....3..1....1..1....0..0....1..0....3..0....2..0....1..3....1..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 04 2011
STATUS
approved