OFFSET
1,2
COMMENTS
Every 0 is next to 0 2's, every 1 is next to 1 2's, every 2 is next to 2 2's, every 3 is next to 3 2's, every 4 is next to 4 2's.
Column 4 of A197061.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) +a(n-3) +2*a(n-4) +3*a(n-5) +2*a(n-6) -a(n-7) -3*a(n-8) -2*a(n-9).
Empirical g.f.: x*(1 + x)*(1 + x + x^2)*(1 + x + 2*x^2 - x^4 - 2*x^5) / (1 - x - x^3 - 2*x^4 - 3*x^5 - 2*x^6 + x^7 + 3*x^8 + 2*x^9). - Colin Barker, May 11 2018
EXAMPLE
Some solutions for n=5:
..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0
..0..1..1..1....0..0..0..0....1..1..1..0....1..1..1..1....1..1..0..0
..1..2..2..2....0..0..0..0....2..2..2..1....2..2..2..2....2..2..1..0
..1..2..4..2....0..0..0..0....2..4..2..1....2..3..3..2....2..2..1..0
..1..2..2..2....0..0..0..0....2..2..2..1....2..2..2..2....1..1..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 09 2011
STATUS
approved