OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
Michael A. Allen, Combinations without specified separations and restricted-overlap tiling with combs, arXiv:2210.08167 [math.CO], 2022.
FORMULA
Empirical: a(n) = a(n-1) + a(n-3) - a(n-4) + 2*a(n-5) - a(n-6) + a(n-7).
Empirical g.f.: x*(1 - x + x^2)*(1 + 2*x + 2*x^2 + x^3 + x^4) / (1 - x - x^3 + x^4 - 2*x^5 + x^6 - x^7). - Colin Barker, Jan 02 2019
EXAMPLE
Some solutions for n=7:
..0....0....0....0....1....0....0....1....1....0....1....1....0....0....1....0
..2....1....2....2....0....1....1....0....0....1....0....0....1....1....0....1
..1....2....1....1....2....2....2....2....2....3....2....3....2....3....3....3
..3....3....3....4....3....3....4....4....4....2....3....2....4....2....2....2
..4....4....5....3....4....4....3....3....3....4....4....4....3....4....4....5
..5....6....4....5....6....5....5....6....5....5....5....6....6....6....5....4
..6....5....6....6....5....6....6....5....6....6....6....5....5....5....6....6
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 24 2015
STATUS
approved