OFFSET
1,1
COMMENTS
Every 0 is next to 0 0's, every 1 is next to 1 0's, every 2 is next to 2 0's, every 3 is next to 3 0's, every 4 is next to 4 0's.
Column 4 of A197054.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) +3*a(n-2) +3*a(n-3) -a(n-4) -2*a(n-5) -a(n-6) for n>7.
Equivalent empirical g.f.: 3*x - 2*x^2*(1+x)*(x^4+3*x^3-3*x-3) / ( 1-x-3*x^2-3*x^3+x^4+2*x^5+x^6 ). - R. J. Mathar, Oct 10 2011
EXAMPLE
Some solutions for n=5
..0..2..1..0....2..0..3..0....0..3..0..2....2..0..3..0....0..3..0..1
..3..0..2..1....0..4..0..3....3..0..4..0....0..4..0..3....2..0..2..1
..0..4..0..2....2..0..4..0....0..4..0..2....3..0..3..0....1..1..2..0
..3..0..4..0....1..2..0..3....3..0..2..1....0..2..1..1....0..3..0..3
..0..3..0..2....0..1..2..0....0..2..1..0....1..1..0..1....2..0..3..0
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
R. H. Hardin, Oct 09 2011
STATUS
approved