OFFSET
1,2
COMMENTS
Column 6 of A221683.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) +5*a(n-2) -7*a(n-3) +33*a(n-4) +17*a(n-5) +24*a(n-6) -5*a(n-7) +2*a(n-8).
Empirical g.f.: x^2*(2 - 3*x + 8*x^2 + 3*x^3 + 6*x^4 - x^5 + x^6) / (1 - 4*x - 5*x^2 + 7*x^3 - 33*x^4 - 17*x^5 - 24*x^6 + 5*x^7 - 2*x^8). - Colin Barker, Oct 19 2017
EXAMPLE
Some solutions for n=6
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....0....0....1....0....0....1....1....1....0....1....1....0....1....0....0
..2....6....3....3....2....1....2....2....2....5....2....3....1....2....0....6
..0....6....3....2....3....5....3....2....1....5....0....3....0....1....3....6
..0....4....6....5....3....4....1....0....5....5....1....3....4....4....2....3
..0....3....5....6....2....3....2....1....5....6....2....3....5....4....1....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 22 2013
STATUS
approved