OFFSET
1,2
COMMENTS
Every 0 is next to 0 2's, every 1 is next to 1 4's, every 2 is next to 2 3's, every 3 is next to 3 0's, every 4 is next to 4 1's.
Column 3 of A196786.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) +2*a(n-2) +4*a(n-3) +3*a(n-4) +6*a(n-5) +2*a(n-6) -2*a(n-7).
Empirical g.f.: x*(1 + x + 9*x^2 - 5*x^3 + 8*x^4 - 4*x^5) / (1 - 2*x - 2*x^2 - 4*x^3 - 3*x^4 - 6*x^5 - 2*x^6 + 2*x^7). - Colin Barker, May 09 2018
EXAMPLE
Some solutions for n=4:
..0..0..0....0..3..0....0..0..0....0..0..0....0..3..0....0..3..0....0..0..0
..0..0..0....0..0..3....3..0..0....3..0..0....3..0..0....3..0..3....0..0..0
..0..0..3....3..0..0....0..0..3....0..0..0....0..0..3....0..0..0....3..0..3
..0..3..0....0..0..0....0..3..0....0..3..0....0..3..0....0..0..0....0..3..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 06 2011
STATUS
approved