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 3's, every 4 is next to 4 4's.
Column 2 of A195978.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) +a(n-3) -a(n-4) -2*a(n-5) -2*a(n-6) -a(n-7).
Empirical g.f.: x*(1 + x)^2*(3 - 3*x - x^2 - 3*x^3 - 2*x^4) / ((1 + x^2)*(1 - x - x^2)*(1 - x - x^2 - x^3)). - Colin Barker, May 08 2018
EXAMPLE
Some solutions for n=4:
..0..1....2..1....1..1....1..0....0..1....1..0....1..2....0..1....0..0....0..1
..1..1....1..0....0..0....1..0....1..1....1..0....0..1....0..1....0..0....0..1
..1..0....1..0....0..0....1..0....1..0....1..1....0..1....1..1....0..0....0..1
..1..0....2..1....1..1....1..0....2..1....0..1....1..2....1..0....0..0....0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 25 2011
STATUS
approved