OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 5*a(n-1) - 3*a(n-2) - 5*a(n-3) - 3*a(n-4) + 3*a(n-5) + 3*a(n-6) + a(n-7).
Empirical g.f.: x*(14 - 24*x - 25*x^2 - 5*x^3 + 22*x^4 + 17*x^5 + 5*x^6) / ((1 - x)*(1 - x - x^2 - x^3)*(1 - 3*x - 3*x^2 - x^3)). - Colin Barker, Nov 01 2018
EXAMPLE
Some solutions for n=4:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....0....1....1....1....0....1....1....1....1....1....1....0....0....1
..2....2....1....1....2....2....0....0....2....2....2....2....1....0....1....0
..3....1....2....2....1....0....1....2....1....2....0....2....0....0....0....0
..0....3....3....3....0....0....1....2....1....2....2....2....2....1....2....2
..3....1....1....3....3....3....2....2....1....3....1....0....0....2....3....1
..2....2....0....0....0....3....2....1....2....2....0....2....1....1....0....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 29 2014
STATUS
approved