OFFSET
1,2
COMMENTS
Every 0 is next to 0 3's, every 1 is next to 1 3's, every 2 is next to 2 2's, every 3 is next to 3 1's, every 4 is next to 4 2's.
Column 3 of A197342.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) +4*a(n-3) +7*a(n-4) +4*a(n-5) +6*a(n-6) +2*a(n-7) -3*a(n-8) -4*a(n-9) -6*a(n-10) -4*a(n-11) +2*a(n-12).
Empirical g.f.: x*(1 + 3*x + x^2 + 12*x^3 + 8*x^5 + 7*x^6 - 8*x^7 - 5*x^8 - 7*x^9 - 6*x^10 + 3*x^11) / (1 - 2*x - 4*x^3 - 7*x^4 - 4*x^5 - 6*x^6 - 2*x^7 + 3*x^8 + 4*x^9 + 6*x^10 + 4*x^11 - 2*x^12). - Colin Barker, May 12 2018
EXAMPLE
Some solutions for n=4:
..2..2..2....0..0..1....1..3..1....0..0..1....1..3..1....2..2..0....0..2..2
..2..0..2....0..1..3....0..1..0....1..1..3....1..1..0....2..2..0....0..2..2
..2..2..2....0..0..1....0..0..0....3..1..1....3..1..0....1..3..1....1..3..1
..0..0..0....0..0..0....0..0..0....1..0..0....1..0..0....0..1..0....0..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 13 2011
STATUS
approved