OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 8*a(n-3) - 11*a(n-6) + 4*a(n-9).
Empirical g.f.: x*(61 + 105*x + 185*x^2 - 161*x^3 - 239*x^4 - 375*x^5 + 76*x^6 + 108*x^7 + 164*x^8) / ((1 - x)*(1 + x + x^2)*(1 - 7*x^3 + 4*x^6)). - Colin Barker, Nov 08 2018
EXAMPLE
Some solutions for n=6:
..3....4....5....2....5....2....4....2....4....4....4....3....5....3....5....6
..2....6....3....6....4....4....2....4....2....3....3....4....3....4....4....4
..4....2....1....4....6....6....0....3....6....5....5....2....4....2....6....5
..3....4....5....2....5....5....1....2....4....1....1....3....2....3....5....3
..5....3....3....3....4....4....2....4....2....3....3....4....6....1....4....1
..1....2....4....4....3....3....3....6....0....2....2....2....4....2....3....2
..3....4....2....5....5....2....4....2....4....1....4....3....5....3....2....3
..5....0....6....3....4....4....5....4....2....0....0....1....3....4....4....4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 06 2014
STATUS
approved