OFFSET
1,2
COMMENTS
Column 2 of A193648
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) +2*a(n-2) +a(n-3).
Empirical: G.f.: -x*(1+3*x+x^2) / ( -1+2*x+2*x^2+x^3 ). - R. J. Mathar, Feb 19 2015
EXAMPLE
Some solutions for n=6
..1....0...-1....0...-1...-2...-2....1....1...-2...-1....2...-1....1....2....0
.-1....0....1...-1....1....2....2...-1...-1....2....1...-2....1...-1...-2....1
..2...-1...-1....1...-2...-2...-1....2....1...-2....2....1....0...-1....2...-1
.-2....1...-2....0....2....0....1...-2...-1....0...-2...-1....1....1...-2....2
.-1...-1....2....1....1....0...-1....0...-2....2....0...-2...-1...-1....2...-2
..1....1....0...-1...-1....0....1....0....2...-2....0....2....0....0...-2....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin Aug 02 2011
STATUS
approved