OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + a(n-3) - a(n-4) + 2*a(n-5) - a(n-6) + a(n-7) for n>18.
Empirical g.f.: x*(1 + x + 4*x^2 + 7*x^3 + 16*x^4 - 3*x^5 - 6*x^6 - 21*x^7 - 9*x^8 - 19*x^9 - x^10 - 5*x^11 + 9*x^12 - 2*x^13 + 6*x^14 - 9*x^15 - 4*x^17) / (1 - x - x^3 + x^4 - 2*x^5 + x^6 - x^7). - Colin Barker, Jan 02 2019
EXAMPLE
Some solutions for n=7:
..1....0....1....1....0....0....0....1....0....1....0....0....2....1....1....0
..0....1....0....0....1....1....1....0....2....0....1....1....0....0....0....1
..4....2....2....3....4....3....3....3....1....3....4....2....1....2....4....2
..2....3....3....4....3....4....4....2....3....4....2....4....4....3....3....4
..3....5....4....2....2....2....2....4....4....2....5....3....3....4....2....5
..6....4....5....6....6....6....5....5....5....5....3....5....5....6....5....3
..5....6....6....5....5....5....6....6....6....6....6....6....6....5....6....6
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 24 2015
STATUS
approved