OFFSET
1,1
COMMENTS
Every 0 is next to 0 3's, every 1 is next to 1 1's, every 2 is next to 2 0's, every 3 is next to 3 2's, every 4 is next to 4 4's.
Column 2 of A196856.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = a(n-1) + 4*a(n-2) + 17*a(n-3) + 10*a(n-4) - 3*a(n-5) + 2*a(n-6) + 2*a(n-7) for n>8.
Empirical g.f.: x*(2 + 9*x + 19*x^2 + 20*x^3 + x^4 + 2*x^5 + x^6 - 6*x^7) / (1 - x - 4*x^2 - 17*x^3 - 10*x^4 + 3*x^5 - 2*x^6 - 2*x^7). - Colin Barker, Mar 01 2018
EXAMPLE
Some solutions for n=4:
..0..0....1..1....1..1....2..0....1..1....1..1....2..0....0..0....2..0....0..0
..1..0....0..0....0..0....0..0....0..2....0..2....0..1....0..0....0..0....2..0
..1..0....2..0....0..1....0..0....2..0....0..0....0..1....2..1....0..1....2..0
..0..0....1..1....0..1....1..1....1..1....0..2....0..0....0..1....0..1....0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 06 2011
STATUS
approved