OFFSET
1,1
COMMENTS
Column 1 of A232038.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 2*a(n-2) + a(n-3) - a(n-4).
Empirical g.f.: x*(3 - x - x^2) / (1 - 4*x + 2*x^2 - x^3 + x^4). - Colin Barker, Mar 19 2018
EXAMPLE
Some solutions for n=7:
..0..0....0..0....0..0....0..1....0..0....0..0....0..0....0..0....0..1....0..0
..0..0....0..0....0..1....0..1....1..1....1..1....0..1....0..0....0..1....0..0
..0..0....1..1....1..0....0..0....1..0....1..0....0..1....0..1....1..1....0..0
..0..0....0..0....0..1....0..0....0..1....1..0....1..0....0..1....1..0....1..1
..1..1....1..1....1..1....1..1....1..0....0..1....1..0....1..1....0..0....1..0
..1..0....0..0....1..1....0..1....1..0....1..1....0..0....1..0....1..0....1..0
..0..0....1..1....1..0....0..0....1..1....0..0....0..1....0..1....1..1....0..0
..1..1....0..0....1..0....0..0....0..0....1..1....0..1....0..1....0..0....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 17 2013
STATUS
approved