OFFSET
1,2
COMMENTS
Column 7 of A221542.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) +4*a(n-2) +5*a(n-3) +20*a(n-4) +20*a(n-5) +23*a(n-6) -6*a(n-7) +3*a(n-8).
Empirical g.f.: x^2*(7 - 5*x + 14*x^2 - 3*x^3 + 20*x^4 - 6*x^5) / (1 - 7*x - 4*x^2 - 5*x^3 - 20*x^4 - 20*x^5 - 23*x^6 + 6*x^7 - 3*x^8). - Colin Barker, Oct 18 2017
EXAMPLE
Some solutions for n=6
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..4....7....6....3....0....4....3....2....0....0....0....2....4....2....3....4
..2....5....3....2....6....1....4....7....3....4....6....6....0....5....2....1
..4....6....6....4....6....4....1....0....6....4....5....6....2....0....0....7
..4....2....7....1....7....3....7....2....3....0....5....6....2....6....4....4
..6....7....5....7....4....6....4....6....0....3....5....1....7....2....0....1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 19 2013
STATUS
approved