OFFSET
1,1
COMMENTS
Column 1 of A206512.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 9*a(n-1) - 18*a(n-2) - 15*a(n-3) + 36*a(n-4) - 20*a(n-5) + 11*a(n-6) - 2*a(n-7).
Empirical g.f.: 3*x*(27 - 60*x - 28*x^2 + 101*x^3 - 59*x^4 + 33*x^5 - 6*x^6) / ((1 - x)*(1 - 4*x + x^2 - x^3)*(1 - 4*x - 7*x^2 + 2*x^3)). - Colin Barker, Jun 17 2018
EXAMPLE
Some solutions for n=4:
..2..2....1..2....1..2....1..2....2..2....2..1....2..1....0..0....1..2....2..0
..1..0....1..2....0..1....1..2....2..1....2..0....0..2....2..1....2..2....2..2
..0..1....2..0....2..2....1..0....2..1....0..1....1..0....0..2....1..2....0..2
..1..2....0..1....1..0....2..1....1..1....0..2....2..1....2..0....1..0....2..0
..0..2....2..2....2..1....1..2....2..1....1..0....1..2....2..1....2..1....1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 08 2012
STATUS
approved