OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 19*a(n-1) - 133*a(n-2) + 461*a(n-3) - 867*a(n-4) + 881*a(n-5) - 468*a(n-6) + 108*a(n-7).
Empirical g.f.: x*(3 - 42*x + 211*x^2 - 516*x^3 + 645*x^4 - 402*x^5 + 108*x^6) / ((1 - x)*(1 - 5*x + 5*x^2 - 2*x^3)*(1 - 13*x + 45*x^2 - 54*x^3)). - Colin Barker, Sep 29 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
..0..1..1....0..0..1....0..1..1....0..0..1....0..0..1....0..0..1....0..0..1
..1..1..1....0..1..0....1..1..2....0..1..1....1..1..0....0..1..0....0..1..2
..0..0..2....1..0..2....1..2..2....0..0..0....0..0..0....1..0..0....1..2..2
..0..2..0....0..2..2....3..3..0....1..1..1....0..0..0....0..0..1....2..3..3
..2..0..2....2..0..0....3..0..0....1..2..2....0..2..2....0..1..1....3..3..2
..0..2..1....0..0..3....2..2..3....2..2..0....2..2..3....1..1..1....2..2..3
..2..1..1....3..3..3....2..3..3....2..0..0....2..3..3....2..2..2....2..3..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 09 2013
STATUS
approved