OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 3*a(n-2) - 3*a(n-3) - 3*a(n-4) + 3*a(n-5) + a(n-6) - a(n-7).
Empirical for n mod 2 = 0: a(n) = (5/12)*n^3 + 3*n^2 + (10/3)*n + 1.
Empirical for n mod 2 = 1: a(n) = (5/12)*n^3 + (11/4)*n^2 + (31/12)*n + (1/4).
Empirical g.f.: x*(6 + 17*x + 3*x^2 - 6*x^3 + x^5 - x^6) / ((1 - x)^4*(1 + x)^3). - Colin Barker, Nov 15 2018
EXAMPLE
Some solutions for n=6:
..0....5....1....6....1....0....0....0....2....3....4....6....1....2....4....0
..0....0....2....2....0....0....3....0....2....0....0....5....5....0....2....0
..5....0....0....3....3....2....0....3....2....3....2....1....0....1....2....5
..1....5....0....1....4....1....6....1....4....6....2....1....0....1....0....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 26 2014
STATUS
approved