OFFSET
1,1
COMMENTS
Column 1 of A206577.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 3*a(n-3) + 2*a(n-5) - a(n-7).
Empirical g.f.: x*(4 - 3*x^2 + 2*x^4 - x^6) / (1 - 4*x + 3*x^3 - 2*x^5 + x^7). - Colin Barker, Feb 20 2018
EXAMPLE
Some solutions for n=4:
..1....1....2....0....0....1....0....3....0....1....1....0....1....2....1....1
..0....3....0....2....1....3....2....0....0....0....1....3....3....0....0....3
..0....2....1....2....1....0....1....3....2....1....0....1....3....1....1....2
..0....1....2....1....3....1....3....1....0....3....3....2....1....0....1....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 09 2012
STATUS
approved