OFFSET
1,2
COMMENTS
Column 1 of A210052
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) -6*a(n-2) -20*a(n-3) -8*a(n-4).
Empirical G.f.: x^2*(3+2*x)^2/((1-3*x-2*x^2)*(1-4*x-4*x^2)). [Colin Barker, Mar 23 2012]
EXAMPLE
Some solutions for n=4
..0..0....0..1....0..1....0..0....0..0....0..0....0..0....0..0....0..1....0..1
..1..0....0..0....0..0....0..1....0..1....0..1....0..1....0..1....0..0....1..1
..1..0....1..0....1..0....0..0....0..1....0..1....1..1....1..1....2..0....1..0
..0..0....0..0....1..1....1..1....0..0....0..0....1..2....0..0....0..2....1..1
..0..2....2..0....1..2....1..2....0..2....2..0....1..1....2..2....2..2....2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 16 2012
STATUS
approved