OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + 5*a(n-2) - 5*a(n-3) - 24*a(n-4) - 2*a(n-5) + 15*a(n-6) + 9*a(n-7).
Empirical g.f.: x*(1 - x - 7*x^2 - 5*x^3 + 11*x^4 + 13*x^5 + 3*x^6) / ((1 - x)*(1 - x - 2*x^2 - x^3)*(1 - x - 6*x^2 - 9*x^3)). - Colin Barker, Sep 28 2018
EXAMPLE
Some solutions for n=7:
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0
..0..1....0..1....0..0....0..0....0..1....0..1....0..1....0..1....0..0....0..1
..1..1....1..1....1..1....0..1....1..1....1..1....1..1....1..1....0..0....1..1
..1..2....2..2....1..1....1..1....1..2....2..2....0..0....1..1....0..0....1..1
..2..2....2..1....1..1....1..2....2..2....2..2....0..0....1..1....0..0....2..2
..3..3....1..1....1..1....2..2....0..0....0..0....0..0....2..2....0..0....2..1
..3..2....1..3....1..1....0..0....0..1....0..0....1..1....2..1....1..1....1..1
..2..2....3..3....1..1....0..0....1..1....0..0....1..1....1..1....1..1....1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 08 2013
STATUS
approved