OFFSET
1,1
COMMENTS
Column 1 of A217457.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + a(n-4).
Empirical g.f.: x*(3 - 3*x + 3*x^2 - x^3) / (1 - 2*x - x^4). - Colin Barker, Feb 19 2018
EXAMPLE
All solutions for n=3:
..1....2....0....2....1....2....0....1....0
..0....0....0....2....1....1....0....1....0
..0....0....2....2....1....1....1....2....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 03 2012
STATUS
approved