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