OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 16*a(n-1) - 21*a(n-2) + 6*a(n-3).
Empirical g.f.: x*(5 - 15*x + 6*x^2) / ((1 - x)*(1 - 15*x + 6*x^2)). - Colin Barker, Oct 07 2018
EXAMPLE
Some solutions for n=5:
..0..0..1....0..0..0....0..1..0....0..0..0....0..0..1....0..0..1....0..0..1
..1..1..1....1..1..1....0..2..0....0..1..0....2..0..0....1..1..1....0..1..0
..0..1..0....0..1..0....2..2..0....3..1..3....0..0..2....3..1..3....1..1..0
..3..2..3....0..2..3....2..2..3....0..2..0....1..0..0....3..2..0....3..1..3
..2..3..2....2..2..2....3..3..2....3..2..2....2..0..2....3..2..3....3..1..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 04 2013
STATUS
approved