OFFSET
1,1
COMMENTS
Column 1 of A209814.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 8*a(n-1) - 7*a(n-2) - 28*a(n-3) - 12*a(n-4).
Empirical g.f.: x*(7 - 22*x - 50*x^2 - 20*x^3) / ((1 + x)*(1 - 6*x)*(1 - 3*x - 2*x^2)). - Colin Barker, Jul 13 2018
EXAMPLE
Some solutions for n=4:
..0..0....0..0....0..0....0..1....0..0....0..0....0..0....0..1....0..0....0..0
..0..1....0..1....1..1....0..0....0..1....0..1....1..0....1..0....0..1....0..1
..1..0....0..1....0..1....0..1....0..0....0..0....0..1....0..1....0..1....1..1
..0..0....0..0....1..0....1..0....0..1....1..0....1..0....1..0....1..0....0..1
..2..2....0..1....0..0....0..0....1..1....1..0....0..1....0..0....0..1....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 13 2012
STATUS
approved