OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (17/2)*n^2 + (29/2)*n + 9.
Conjectures from Colin Barker, Nov 17 2018: (Start)
G.f.: x*(32 - 24*x + 9*x^2) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>3.
(End)
EXAMPLE
Some solutions for n=4:
..1..1..1..1..0....0..0..0..1..0....0..0..0..1..1....2..2..1..1..0
..1..1..1..1..2....0..0..0..1..2....1..1..1..2..2....0..0..1..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 27 2014
STATUS
approved