OFFSET
1,2
COMMENTS
Column 1 of A204685.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) + a(n-2) - 6*a(n-3) - 3*a(n-4) for n>6.
Empirical g.f.: x*(1 + x)*(1 - 3*x - 2*x^2 + 2*x^3 + x^4) / ((1 - x - x^2)*(1 - 3*x - 3*x^2)). - Colin Barker, Feb 19 2018
EXAMPLE
Some solutions for n=5:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....1....0....1....0....0....1....0....1....0....0....0....1....1....0
..1....2....0....1....0....1....1....0....1....1....1....1....1....0....0....1
..0....1....2....0....0....0....0....1....0....0....0....1....0....0....0....0
..0....0....0....0....1....2....0....0....0....0....0....0....1....1....1....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 18 2012
STATUS
approved