OFFSET
1,1
COMMENTS
Column 2 of A206343.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 3*a(n-2) - 3*a(n-3) for n>11.
Empirical g.f.: x*(96 + 85*x - 237*x^2 + 47*x^3 - x^4 - 3*x^5 - 3*x^6 + 2*x^9 + 2*x^10) / ((1 - x)*(1 - 3*x^2)). - Colin Barker, Jun 15 2018
EXAMPLE
Some solutions for n=4:
..3..0..1....0..1..0....1..3..1....0..2..0....0..1..0....1..0..1....0..1..0
..0..3..0....3..0..1....3..1..3....3..0..2....1..0..1....0..1..0....3..0..1
..2..0..3....0..3..0....1..3..1....0..3..0....0..1..0....2..0..1....0..3..0
..0..2..0....1..0..3....3..1..3....1..0..3....2..0..1....0..2..0....3..0..3
..1..0..2....0..1..0....1..3..1....0..1..3....0..2..1....1..0..2....0..3..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 06 2012
STATUS
approved