OFFSET
1,1
COMMENTS
Every 0 is next to 0 3's, every 1 is next to 1 0's, every 2 is next to 2 2's, every 3 is next to 3 4's, every 4 is next to 4 1's.
Column 2 of A196456.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) +3*a(n-3) -2*a(n-4) -3*a(n-5) -5*a(n-6) -a(n-7).
Empirical g.f.: x*(3 + 2*x^2 - 7*x^3 - 5*x^4 - 9*x^5 - x^6) / (1 - 2*x - 3*x^3 + 2*x^4 + 3*x^5 + 5*x^6 + x^7). - Colin Barker, May 09 2018
EXAMPLE
Some solutions for n=4:
..1..0....2..2....1..0....1..1....1..0....0..1....1..0....2..2....2..2....0..0
..1..0....2..2....1..0....0..0....2..2....2..2....2..2....2..2....2..2....0..0
..1..0....0..1....1..1....0..0....2..2....2..2....2..2....1..0....0..0....0..0
..1..0....0..1....0..1....1..1....0..0....0..1....0..1....1..0....1..1....1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 02 2011
STATUS
approved