OFFSET
1,1
COMMENTS
Every 0 is next to 0 2's, every 1 is next to 1 0's, every 2 is next to 2 1's, every 3 is next to 3 1's, every 4 is next to 4 1's.
Column 2 of A197280.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) +2*a(n-3) -2*a(n-4) -2*a(n-5) -a(n-6) -2*a(n-7).
Empirical g.f.: (1 + x)^2*(3 - 3*x - x^2 - 2*x^4) / (1 - 2*x - 2*x^3 + 2*x^4 + 2*x^5 + x^6 + 2*x^7). - Colin Barker, May 11 2018
EXAMPLE
Some solutions for n=4:
..2..1....0..0....0..1....0..1....2..1....0..0....2..1....1..0....1..0....0..1
..1..0....0..0....1..1....0..1....1..0....1..1....1..0....3..1....1..0....1..3
..1..0....0..0....1..0....0..1....1..0....1..1....1..1....1..1....1..0....1..1
..2..1....0..0....2..1....1..2....1..0....0..0....0..1....0..0....1..0....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 12 2011
STATUS
approved