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 1's, every 4 is next to 4 4's.
Column 2 of A196485.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) + 4*a(n-3) - 3*a(n-4) - 3*a(n-5) - a(n-6) + a(n-7) -a(n-8).
Empirical g.f.: x*(3 + 2*x^2 - 4*x^3 - 4*x^4 - 3*x^5 + 3*x^6 - 3*x^7) / (1 - 2*x - 4*x^3 + 3*x^4 + 3*x^5 + x^6 - x^7 + x^8). - Colin Barker, Mar 01 2018
EXAMPLE
Some solutions for n=4:
..0..0....0..0....2..2....0..0....1..1....2..2....1..0....0..0....0..0....1..1
..0..0....1..1....2..2....2..2....0..0....2..2....1..0....1..1....0..0....0..0
..0..0....2..2....0..0....2..2....2..2....0..0....1..0....3..1....2..2....0..0
..0..0....2..2....0..0....1..0....2..2....1..1....1..0....1..0....2..2....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 03 2011
STATUS
approved