OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (2/45)*n^6 + (8/15)*n^5 + (115/36)*n^4 + 8*n^3 + (1667/180)*n^2 + (149/30)*n + 1.
Conjectures from Colin Barker, Sep 11 2018: (Start)
G.f.: x*(27 - 6*x + 22*x^2 - 27*x^3 + 22*x^4 - 7*x^5 + x^6) / (1 - x)^7.
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.
(End)
EXAMPLE
Some solutions for n=4:
..4....4....4....3....1....4....4....4....4....1....4....4....0....1....2....0
..2....4....4....1....0....2....2....2....2....0....4....2....1....1....1....0
..0....4....4....0....2....0....1....3....1....0....2....0....1....1....1....0
..0....3....1....1....3....0....3....3....0....2....2....1....2....0....0....1
..0....3....0....4....3....0....4....3....3....2....2....1....3....0....1....1
..2....3....4....4....3....1....4....3....4....3....2....1....4....4....2....4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 22 2013
STATUS
approved