OFFSET
1,2
COMMENTS
Every 0 is next to 0 4's, every 1 is next to 1 3's, every 2 is next to 2 0's, every 3 is next to 3 1's, every 4 is next to 4 2's.
Column 2 of A197235.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = a(n-1) +3*a(n-2) +2*a(n-3) -a(n-4) -a(n-5) -a(n-6).
Empirical g.f.: x*(1 + 6*x + 2*x^2 - 4*x^3 - x^4 - 2*x^5) / (1 - x - 3*x^2 - 2*x^3 + x^4 + x^5 + x^6). - Colin Barker, Feb 18 2018
EXAMPLE
Some solutions for n=4:
..0..2....0..0....0..0....0..0....2..0....0..2....2..0....0..0....0..1....0..0
..0..0....0..2....2..2....0..0....0..0....0..0....0..2....0..1....1..3....0..0
..0..0....0..2....0..0....0..0....2..2....0..0....0..2....1..3....0..1....0..0
..0..0....0..0....0..2....2..0....0..0....2..0....2..0....0..1....0..0....0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 12 2011
STATUS
approved