OFFSET
1,2
COMMENTS
Every 0 is next to 0 4's, every 1 is next to 1 2's, every 2 is next to 2 1's, every 3 is next to 3 0's, every 4 is next to 4 3's.
Column 2 of A197207.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) + 4*a(n-2) + 2*a(n-3) - 4*a(n-4) - 8*a(n-5) + a(n-7) + 2*a(n-8).
Empirical g.f.: x*(1 + x)*(1 + 2*x - 7*x^3 - 3*x^4 - x^5 + 4*x^6) / (1 - 2*x - 4*x^2 - 2*x^3 + 4*x^4 + 8*x^5 - x^7 - 2*x^8). - Colin Barker, Mar 01 2018
EXAMPLE
Some solutions for n=4:
..0..0....0..0....2..1....0..0....1..0....0..1....0..0....1..2....1..2....0..0
..0..0....3..0....1..0....0..0....2..0....1..2....0..0....0..1....0..1....0..3
..0..0....0..3....0..0....0..1....1..1....0..0....1..2....2..1....3..0....3..0
..0..0....0..0....0..0....1..2....1..2....0..0....0..1....1..0....0..0....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 11 2011
STATUS
approved