OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + 3*a(n-2).
Conjectures from Colin Barker, Oct 24 2018: (Start)
G.f.: 12*x / (1 - 3*x - 3*x^2).
a(n) = (-4)*(sqrt(3/7)*(((3-sqrt(21))/2)^n - ((3+sqrt(21))/2)^n)).
(End)
EXAMPLE
Some solutions for n=5:
..0..0....1..1....3..3....2..2....2..2....1..1....0..0....3..3....3..3....2..2
..3..3....2..2....2..2....0..0....1..1....0..0....1..1....1..1....1..1....3..3
..2..2....3..3....0..0....2..2....2..2....2..2....0..0....2..2....0..0....2..2
..0..0....2..2....1..1....3..3....2..2....2..2....1..1....2..2....1..1....3..3
..0..0....3..3....1..1....2..2....0..0....3..3....0..0....3..3....0..0....2..2
..2..2....1..1....0..0....0..0....1..1....1..1....3..3....0..0....1..1....1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 07 2014
STATUS
approved