OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 9*a(n-1) - 10*a(n-2) - 50*a(n-3).
Conjectures from Colin Barker, Jan 22 2019: (Start)
G.f.: 6*x*(1 - 3*x - 9*x^2) / ((1 - 5*x)*(1 - 4*x - 10*x^2)).
a(n) = (-84*5^n + (231-57*sqrt(14))*(2-sqrt(14))^n + 3*(2+sqrt(14))^n*(77+19*sqrt(14))) / 350.
(End)
EXAMPLE
Some solutions for n=6:
..0. .4. .1. .4. .3. .2. .1. .3. .4. .3. .0. .2. .2. .3. .2. .0
..3. .3. .2. .1. .5. .1. .2. .3. .2. .2. .3. .0. .3. .5. .4. .1
..0. .4. .3. .4. .5. .0. .2. .1. .4. .5. .2. .3. .0. .5. .5. .1
..2. .1. .1. .4. .2. .5. .5. .4. .2. .5. .3. .2. .0. .1. .5. .3
..1. .3. .4. .2. .3. .1. .1. .3. .4. .2. .0. .4. .1. .0. .1. .0
..4. .3. .3. .5. .2. .0. .4. .1. .5. .5. .3. .4. .0. .3. .0. .0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 27 2016
STATUS
approved