OFFSET
1,1
COMMENTS
Every 0 is next to 0 4's, every 1 is next to 1 1's, every 2 is next to 2 2's, every 3 is next to 3 0's, every 4 is next to 4 3's.
Column 2 of A196967.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) +3*a(n-2) +2*a(n-3) -5*a(n-5) -3*a(n-6) +2*a(n-7).
Empirical g.f.: x*(2 + 2*x - 3*x^2 - 4*x^3 - 8*x^4 - 5*x^5 + 4*x^6) / ((1 - x)*(1 - x - 4*x^2 - 6*x^3 - 6*x^4 - x^5 + 2*x^6)). - Colin Barker, May 10 2018
EXAMPLE
Some solutions for n=4:
..0..1....2..2....0..0....0..0....0..0....0..0....2..2....0..0....1..0....0..0
..0..1....2..2....2..2....3..0....0..0....3..0....2..2....0..0....1..0....0..3
..0..0....0..1....2..2....0..3....2..2....0..1....0..0....1..1....2..2....0..0
..0..0....0..1....1..1....0..0....2..2....0..1....1..1....0..0....2..2....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 08 2011
STATUS
approved