OFFSET
1,2
COMMENTS
Every 0 is next to 0 1's, every 1 is next to 1 2's, every 2 is next to 2 3's, every 3 is next to 3 0's, every 4 is next to 4 4's.
Column 4 of A196578.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 2*a(n-1) +9*a(n-2) +39*a(n-3) +20*a(n-4) +12*a(n-5) +32*a(n-6) -17*a(n-7) +a(n-8) -4*a(n-9) +a(n-10).
Empirical g.f.: x*(1 + 5*x + 14*x^2 - 31*x^3 + 55*x^4 - 55*x^5 + 13*x^6 - 10*x^7 + x^8 + x^9) / (1 - 2*x - 9*x^2 - 39*x^3 - 20*x^4 - 12*x^5 - 32*x^6 + 17*x^7 - x^8 + 4*x^9 - x^10). - Colin Barker, May 09 2018
EXAMPLE
Some solutions for n=5:
..0..0..0..0....0..0..3..0....0..3..0..0....0..0..0..0....0..0..3..0
..0..3..0..0....3..0..0..3....0..0..0..0....0..0..0..3....0..0..0..0
..0..3..0..0....0..0..0..0....0..3..3..0....0..3..2..0....0..0..0..0
..0..0..0..0....0..0..0..3....3..0..0..0....0..0..3..0....0..0..0..0
..0..3..0..0....0..0..0..0....0..3..0..0....0..3..0..0....0..0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 04 2011
STATUS
approved