OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-3) - 7*a(n-6) + 2*a(n-9) for n>12.
Empirical g.f.: x*(206 + 185*x + 232*x^2 - 914*x^3 - 575*x^4 - 540*x^5 + 770*x^6 + 306*x^7 + 188*x^8 - 180*x^9 - 40*x^10 + 2*x^11) / ((1 - x)*(1 + x + x^2)*(1 - 5*x^3 + 2*x^6)). - Colin Barker, Dec 03 2018
EXAMPLE
Some solutions for n=4:
..2..3..0....0..3..2....3..2..3....2..3..0....3..0..2....3..2..0....2..1..2
..1..2..2....3..3..2....2..1..2....2..3..3....2..2..1....0..0..1....3..2..3
..2..3..3....2..2..1....3..2..0....1..2..2....3..3..2....2..3..0....0..2..3
..2..3..3....3..3..2....3..2..3....2..3..3....3..0..2....3..2..0....2..1..2
..1..2..2....0..3..2....2..1..2....2..0..3....2..2..1....0..0..0....3..2..3
..2..0..3....2..2..1....0..2..3....1..2..2....0..3..2....2..3..0....3..2..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 16 2014
STATUS
approved