OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 12*a(n-1) - 36*a(n-2) - 22*a(n-3) + 140*a(n-4) - 48*a(n-5) - 121*a(n-6) + 88*a(n-7) - 16*a(n-8).
Empirical g.f.: 4*x^2*(1 - x)*(1 - 3*x + x^2)*(1 + x + 4*x^2) / (1 - 6*x + 11*x^3 - 4*x^4)^2. - Colin Barker, Feb 11 2019
EXAMPLE
Some solutions for n=4:
..0..1..2..1. .0..0..1..2. .0..1..1..2. .0..0..1..0. .0..1..0..2
..0..1..1..2. .1..0..0..1. .2..1..0..1. .1..0..1..2. .1..1..0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 15 2016
STATUS
approved