OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 2*a(n-2) + 6*a(n-3) + 5*a(n-4) + a(n-5) - 2*a(n-6) - 2*a(n-7) - a(n-8) for n>9.
Empirical g.f.: 2*x*(76 + 62*x + 127*x^2 + 20*x^3 - 62*x^4 - 85*x^5 - 36*x^6 - x^7 + 16*x^8) / (1 - x - 2*x^2 - 6*x^3 - 5*x^4 - x^5 + 2*x^6 + 2*x^7 + x^8). - Colin Barker, Dec 03 2018
EXAMPLE
Some solutions for n=4:
..0..2..0..0....0..0..0..0....3..3..3..3....0..2..0..0....3..3..2..3
..2..0..0..0....0..2..0..0....3..3..3..2....0..0..0..0....3..3..3..2
..0..0..0..0....0..0..0..2....3..3..3..3....0..0..0..0....3..3..3..3
..0..0..0..0....0..0..0..0....3..3..2..3....0..0..0..0....3..3..2..3
..0..2..0..0....2..0..0..0....2..3..3..3....2..0..0..2....3..3..3..3
..0..0..0..2....0..0..0..0....3..3..3..3....0..0..2..0....3..3..3..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 17 2014
STATUS
approved