OFFSET
1,1
COMMENTS
Every 0 is next to 0 4's, every 1 is next to 1 0's, every 2 is next to 2 1's, every 3 is next to 3 0's, every 4 is next to 4 1's.
Column 2 of A197672.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 3*a(n-1) +4*a(n-2) -25*a(n-4) -37*a(n-5) +4*a(n-6) +23*a(n-7) +17*a(n-8) -5*a(n-9) -a(n-10).
Empirical g.f.: x*(1 - x)*(1 + x)^2*(3 - 3*x - 11*x^2 - 20*x^3 - 3*x^4 + 15*x^5 + 2*x^6) / ((1 - x - 5*x^2 - 4*x^3 - x^4 + x^5)*(1 - 2*x - x^2 - 7*x^3 + 6*x^4 + x^5)). - Colin Barker, May 14 2018
EXAMPLE
Some solutions for n=4:
..2..1....0..0....1..0....2..1....0..1....1..0....0..0....0..1....1..0....0..0
..1..0....3..0....1..0....1..0....2..1....2..1....1..2....1..2....1..1....0..0
..1..0....0..0....1..1....1..1....1..0....0..2....1..1....2..0....0..1....0..0
..1..0....0..0....0..1....0..1....1..0....0..1....0..0....1..0....0..1....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 17 2011
STATUS
approved