OFFSET
1,1
COMMENTS
Column 1 of A239340.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) +2*a(n-3).
Empirical g.f.: (2 + x + 2*x^2) / (1 - 2*x - 2*x^3). - Colin Barker, Feb 18 2018
EXAMPLE
Some solutions for n=5:
..0....2....2....2....0....0....0....0....2....2....2....2....2....0....2....2
..2....0....2....0....2....0....2....0....0....0....0....2....2....2....0....3
..2....2....2....3....2....2....3....0....2....2....3....0....0....0....3....2
..0....0....0....2....2....2....2....0....2....2....3....0....2....0....2....3
..2....2....2....0....2....0....0....0....3....0....2....2....3....2....3....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 16 2014
STATUS
approved