OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/30)*n^5 + (1/24)*n^4 + (23/12)*n^3 - (193/24)*n^2 + (581/20)*n - 30 for n>2.
Conjectures from Colin Barker, Oct 27 2018: (Start)
G.f.: x*(4 - 9*x + 18*x^2 - 18*x^3 + 14*x^4 - 6*x^5 - x^6 + 2*x^7) / (1 - x)^6.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>8.
(End)
EXAMPLE
Some solutions for n=4:
..0..0....0..3....0..3....3..3....3..0....0..0....0..3....0..3....0..3....0..3
..3..3....0..0....0..3....0..3....0..3....3..0....3..2....3..3....3..3....0..0
..3..2....3..3....3..2....3..3....3..3....0..3....3..2....3..3....0..3....3..0
..3..2....0..3....0..3....3..2....3..3....0..0....3..3....3..2....0..0....3..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 04 2014
STATUS
approved