OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 13*a(n-1) - 33*a(n-2) - 63*a(n-3).
Conjectures from Colin Barker, Jan 26 2019: (Start)
G.f.: 8*x*(1 - 5*x - 8*x^2) / ((1 - 7*x)*(1 - 6*x - 9*x^2)).
a(n) = (-216*7^n + (140-98*sqrt(2))*(3-3*sqrt(2))^n + 14*(3*(1+sqrt(2)))^n*(10+7*sqrt(2))) / 63.
(End)
EXAMPLE
Some solutions for n=5:
..2. .6. .5. .0. .3. .6. .2. .1. .6. .0. .3. .3. .2. .7. .6. .3
..2. .0. .2. .7. .6. .2. .0. .5. .4. .5. .0. .0. .5. .6. .3. .4
..3. .2. .4. .6. .0. .1. .3. .4. .2. .2. .5. .6. .7. .5. .0. .5
..0. .2. .7. .2. .0. .2. .0. .5. .4. .3. .0. .4. .1. .7. .0. .6
..6. .7. .6. .6. .4. .6. .2. .1. .6. .2. .4. .3. .3. .4. .1. .1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 03 2016
STATUS
approved