OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + 7*a(n-2) + 6*a(n-3) - 2*a(n-4) - 3*a(n-5) + 2*a(n-6) + a(n-7).
Empirical g.f.: 2*x*(1 + 5*x + 8*x^2 + 2*x^3 - 6*x^4 + x^5 + x^6) / ((1 + x)*(1 - 3*x - 4*x^2 - 2*x^3 + 4*x^4 - x^5 - x^6)). - Colin Barker, Oct 05 2018
EXAMPLE
Some solutions for n=7:
..2..1....0..3....3..2....3..0....3..0....2..3....3..0....1..0....3..2....3..1
..0..3....2..1....1..2....1..2....1..0....0..1....1..0....1..2....1..0....2..1
..0..3....0..1....1..0....3..2....3..2....0..3....1..2....3..2....1..2....2..3
..2..1....2..1....3..0....1..2....1..2....2..3....3..0....3..2....3..2....2..3
..3..1....2..3....2..1....0..3....0..3....0..1....3..2....1..2....3..1....0..1
..0..2....2..1....2..3....0..1....2..1....3..2....1..0....3..0....2..1....0..1
..3..2....0..1....2..3....2..3....3..1....3..2....3..0....1..2....0..3....2..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 23 2013
STATUS
approved