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 + 17*x^3 + 95*x^4 - 54*x^5 - 39*x^6 - 107*x^7 + 22*x^8 - 156*x^9 + 24*x^10 - 58*x^11 - 2*x^12 - 8*x^13 - 2*x^14 - 28*x^15 - 12*x^16 - 16*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:
..0....0....0....0....0....1....0....0....1....4....0....0....0....0....0....0
..4....2....3....1....1....0....1....1....0....0....1....4....1....3....1....1
..1....1....1....2....2....3....4....3....2....1....4....1....3....1....3....2
..2....3....2....4....4....2....2....2....3....3....2....2....4....4....2....3
..3....5....4....5....3....4....5....5....4....2....3....5....2....2....4....4
..5....4....5....6....6....5....3....6....5....5....5....3....5....5....6....5
..6....6....6....3....5....6....6....4....6....6....6....6....6....6....5....6
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 24 2015
STATUS
approved