OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-5) - 3*a(n-6).
Empirical g.f.: x*(2 - 3*x - x^2 - x^3 - 2*x^4 - 3*x^5) / ((1 - x)*(1 - 3*x)*(1 + x + x^2 + x^3 + x^4)). - Colin Barker, Jan 01 2019
EXAMPLE
Some solutions for n=4:
..0..0....2..1....0..0....4..2....0..0....4..2....4..2....0..0....0..0....0..0
..0..0....0..0....0..0....2..1....4..2....2..1....2..1....4..2....2..1....0..0
..4..2....4..2....0..0....0..0....2..1....4..2....0..0....2..1....4..2....0..0
..2..1....2..1....4..2....4..2....4..2....2..1....0..0....0..0....0..0....0..0
..0..0....4..2....2..1....2..1....2..1....0..0....0..0....0..0....2..1....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 19 2015
STATUS
approved