OFFSET
1,2
COMMENTS
Every 0 is next to 0 2's, every 1 is next to 1 3's, every 2 is next to 2 1's, every 3 is next to 3 0's, every 4 is next to 4 4's.
Column 3 of A196746.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) +5*a(n-2) +12*a(n-3) +2*a(n-4) -11*a(n-5) +4*a(n-6) -5*a(n-7) +a(n-8).
Empirical g.f.: x*(1 + x + 9*x^2 + 4*x^3 + 2*x^4 - 10*x^5 - 2*x^6 + 2*x^7) / (1 - 2*x - 5*x^2 - 12*x^3 - 2*x^4 + 11*x^5 - 4*x^6 + 5*x^7 - x^8). - Colin Barker, May 09 2018
EXAMPLE
Some solutions for n=4:
..0..3..0....0..3..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0
..0..0..0....0..0..0....0..0..0....0..0..0....0..1..0....0..0..0....0..3..1
..0..0..0....3..0..3....0..3..1....3..0..0....0..3..0....0..0..3....0..0..0
..0..0..0....0..3..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 06 2011
STATUS
approved