OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 40*n^2 - 199*n + 283 for n>3.
Conjectures from Colin Barker, Dec 06 2018: (Start)
G.f.: x*(4 + x + 17*x^2 + 30*x^3 + 26*x^4 + 2*x^5) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>6.
(End)
EXAMPLE
Some solutions for n=4:
..0..1..2....0..0..0....0..1..1....0..1..1....0..1..2....0..0..1....0..0..0
..0..1..2....0..0..1....1..1..2....1..1..1....1..1..2....1..1..1....0..0..1
..1..1..2....1..1..1....1..1..2....1..2..2....2..2..2....1..1..2....0..1..1
..2..2..2....2..2..2....1..2..2....1..2..3....3..3..3....1..1..2....1..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 22 2014
STATUS
approved