OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) - a(n-3) + a(n-4) - a(n-5) - a(n-6) + a(n-7).
Empirical g.f.: 2*x*(44 - 20*x - 26*x^2 + 6*x^3 - 38*x^4 - 9*x^5 + 32*x^6) / ((1 - x)*(1 - x - x^2 - x^4 + x^6)). - Colin Barker, Nov 07 2018
EXAMPLE
Some solutions for n=6:
..2....0....2....0....0....2....3....3....2....2....0....1....3....3....0....2
..3....1....0....1....1....3....2....2....1....1....1....1....0....3....1....1
..1....3....1....1....3....1....2....1....2....1....0....0....0....2....1....0
..0....2....3....2....2....2....1....2....3....2....1....2....3....2....2....3
..2....2....2....2....0....0....1....1....2....2....2....1....3....1....0....2
..1....1....0....1....1....1....2....2....1....1....1....3....0....3....1....1
..1....1....1....3....1....1....0....1....2....3....2....0....0....2....1....2
..0....0....1....0....0....2....1....0....3....0....1....2....3....2....2....3
..2....2....2....2....0....2....3....1....2....2....2....1....3....3....0....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 18 2014
STATUS
approved