OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 7*a(n-1) - 4*a(n-2) - 32*a(n-3).
Empirical g.f.: 5*x*(1 - 2*x - 7*x^2) / ((1 - 4*x)*(1 - 3*x - 8*x^2)). - Colin Barker, Jan 22 2019
EXAMPLE
Some solutions for n=7:
..1. .3. .0. .3. .3. .2. .2. .2. .1. .2. .0. .1. .2. .0. .1. .0
..4. .1. .0. .0. .4. .0. .4. .4. .0. .3. .4. .4. .2. .4. .2. .3
..3. .0. .2. .2. .0. .4. .3. .4. .1. .0. .0. .2. .3. .1. .3. .1
..0. .1. .1. .1. .4. .1. .3. .3. .4. .0. .2. .3. .3. .0. .2. .4
..1. .0. .3. .4. .1. .4. .1. .2. .4. .2. .0. .4. .1. .1. .1. .0
..4. .4. .4. .2. .0. .0. .2. .0. .0. .2. .1. .4. .4. .3. .1. .3
..1. .2. .2. .3. .3. .2. .4. .0. .0. .1. .4. .1. .1. .2. .4. .3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 27 2016
STATUS
approved