OFFSET
1,1
COMMENTS
Every 0 is next to 0 1's, every 1 is next to 1 3's, every 2 is next to 2 0's, every 3 is next to 3 4's, every 4 is next to 4 2's.
Column 3 of A196329.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = a(n-1) +3*a(n-2) +5*a(n-3) +3*a(n-4) -a(n-5) +a(n-6) -2*a(n-8) -a(n-9).
Empirical g.f.: x*(2 + 8*x + 11*x^2 + x^3 + x^4 - 8*x^6 - 6*x^7 - x^8) / ((1 + x)*(1 - 2*x - x^2 - 4*x^3 + x^4 - x^6 + x^7 + x^8)). - Colin Barker, May 08 2018
EXAMPLE
Some solutions for n=4:
..0..0..0....0..2..0....0..2..0....2..0..0....2..0..2....2..0..0....0..0..2
..0..0..0....0..2..0....0..2..2....0..0..0....0..0..0....0..2..2....0..0..0
..2..2..0....2..4..2....0..0..0....0..0..0....0..0..0....0..2..0....0..0..0
..0..2..0....0..2..0....0..0..0....2..0..0....0..0..0....0..2..0....2..0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 01 2011
STATUS
approved