OFFSET
1,1
COMMENTS
Column 2 of A220810.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) - 11*a(n-2) - 3*a(n-3) - 4*a(n-4).
Empirical g.f.: 2*x*(1 - 3*x + 2*x^2 - 2*x^3) / ((1 - 4*x)*(1 - 3*x - x^2 - x^3)). - Colin Barker, Mar 13 2018
EXAMPLE
Some solutions for n=3:
..0..0....0..0....1..1....0..0....1..0....0..1....0..0....0..1....0..0....1..0
..0..0....0..1....1..0....1..0....1..0....1..0....0..0....0..0....0..0....0..0
..1..0....1..0....0..1....1..0....0..0....1..1....0..0....1..0....1..1....1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 22 2012
STATUS
approved