OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 44*a(n-1) - 556*a(n-2) + 1616*a(n-3) - 2000*a(n-4) + 1152*a(n-5) - 256*a(n-6) for n>7.
Empirical g.f.: 2*x*(1 - 2*x)^2*(1 - 22*x + 144*x^2 - 176*x^3 + 64*x^4) / (1 - 22*x + 36*x^2 - 16*x^3)^2. - Colin Barker, Feb 11 2019
EXAMPLE
Some solutions for n=4:
..0..0..1. .0..1..2. .0..1..2. .0..1..2. .0..0..1. .0..1..1. .0..0..1
..2..0..0. .1..1..0. .2..1..2. .1..0..2. .1..1..0. .2..2..1. .2..1..0
..1..1..0. .2..1..1. .1..0..1. .2..1..1. .0..1..2. .0..2..0. .2..2..2
..0..1..0. .2..0..2. .0..2..2. .1..2..2. .2..1..2. .2..2..1. .0..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 15 2016
STATUS
approved