OFFSET
1,1
COMMENTS
Column 3 of A203362.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) +12*a(n-2) +6*a(n-3) +a(n-4).
Empirical g.f.: x*(3 + 11*x + 6*x^2 + x^3) / (1 - 3*x - 12*x^2 - 6*x^3 - x^4). - Colin Barker, Jun 04 2018
EXAMPLE
Some solutions for n=5:
..0..1..0....0..1..0....0..0..0....0..0..0....0..0..1....0..0..1....0..1..0
..0..0..0....0..0..0....0..0..1....0..1..1....1..0..1....1..0..0....0..1..0
..0..0..1....0..0..1....1..1..0....0..1..0....0..0..0....0..1..0....0..0..1
..0..0..0....0..0..1....0..1..0....1..0..1....1..0..0....0..1..0....0..1..0
..0..1..0....0..1..0....0..1..0....0..0..0....0..0..0....0..1..0....0..1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 31 2011
STATUS
approved