OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + 5*a(n-2) + a(n-3) for n>4.
Conjectures from Colin Barker, Jan 31 2019: (Start)
G.f.: 8*x*(1 + 15*x + 7*x^2 + x^3) / ((1 + x)*(1 - 4*x - x^2)).
a(n) = 8*(2*(-1)^n - (2*((2-sqrt(5))^n - (2+sqrt(5))^n))/sqrt(5)) for n>1.
(End)
EXAMPLE
Some solutions for n=5:
..0..1..2..1..0. .0..1..0..2..1. .0..1..0..1..0. .0..1..2..1..2
..2..1..2..0..1. .1..2..1..0..1. .2..1..2..0..2. .0..1..2..0..1
..2..0..1..2..1. .1..0..2..0..2. .2..0..1..2..1. .2..0..1..0..1
..1..0..1..2..0. .2..1..2..1..0. .1..0..1..2..0. .2..0..1..2..0
..1..2..0..2..0. .2..1..0..2..0. .1..2..0..1..0. .2..1..0..2..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jul 17 2016
STATUS
approved