OFFSET
1,1
COMMENTS
Column 4 of A217883.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + 3*a(n-5) - a(n-6) + a(n-7) + a(n-8) + a(n-9).
Empirical g.f.: x*(1 + x^2 + x^3 + x^4)*(3 + x^2 + x^3 + x^4) / (1 - 3*x + 3*x^2 - x^3 - 3*x^5 + x^6 - x^7 - x^8 - x^9). - Colin Barker, Jul 23 2018
EXAMPLE
Some solutions for n=4:
..2....0....1....1....2....0....1....1....1....1....1....2....1....0....0....2
..2....0....1....2....2....1....1....2....1....1....1....1....2....2....1....2
..1....1....2....1....0....2....2....0....1....0....2....0....2....2....1....2
..0....1....1....0....0....2....2....0....2....0....0....0....2....0....2....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 14 2012
STATUS
approved