OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 10*a(n-1) - 21*a(n-2) - 20*a(n-3).
Conjectures from Colin Barker, Jan 27 2019: (Start)
G.f.: 6*x*(1 - 4*x - 3*x^2) / ((1 - 5*x)*(1 - 5*x - 4*x^2)).
a(n) = (3/205)*2^(-2-n)*(-41*2^(2+n)*5^n-5*(5-sqrt(41))^n*(-41+7*sqrt(41)) + 5*(5+sqrt(41))^n*(41+7*sqrt(41))).
(End)
EXAMPLE
Some solutions for n=6:
..2. .2. .2. .5. .2. .0. .4. .4. .4. .0. .1. .5. .3. .1. .3. .4
..3. .2. .3. .2. .1. .4. .1. .5. .5. .3. .4. .5. .5. .4. .5. .3
..4. .1. .1. .0. .2. .5. .1. .2. .2. .5. .0. .2. .1. .0. .2. .4
..5. .5. .5. .4. .1. .4. .2. .4. .4. .2. .5. .4. .1. .4. .1. .0
..5. .1. .2. .2. .5. .5. .1. .1. .5. .1. .3. .3. .3. .0. .3. .5
..4. .5. .4. .4. .5. .0. .1. .1. .4. .5. .2. .1. .2. .1. .2. .4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 03 2016
STATUS
approved