OFFSET
1,1
COMMENTS
Column 1 of A209913.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) + 21*a(n-2) - 30*a(n-3) - 30*a(n-4) + 12*a(n-5) + 8*a(n-6).
Empirical g.f.: 2*x*(31 + 64*x - 114*x^2 - 114*x^3 + 46*x^4 + 32*x^5) / (1 - 7*x - 21*x^2 + 30*x^3 + 30*x^4 - 12*x^5 - 8*x^6). - Colin Barker, Jul 13 2018
EXAMPLE
Some solutions for n=4:
..0..2....1..2....0..2....2..0....0..0....0..0....3..0....2..0....2..3....1..0
..0..3....0..3....3..3....2..3....1..3....2..3....1..0....3..0....0..1....0..1
..0..1....2..2....0..1....1..2....2..1....3..2....0..3....2..0....2..0....0..3
..2..3....0..3....2..3....0..1....3..2....0..1....2..3....3..1....0..1....1..2
..1..2....2..2....2..0....1..2....0..3....0..3....1..2....1..2....3..0....2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 15 2012
STATUS
approved