OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - 3*a(n-3) - a(n-4) for n>5.
Empirical g.f.: 2*x^2*(1 - x)*(1 - 2*x - x^2) / (1 - 4*x + 2*x^2 + 3*x^3 + x^4). - Colin Barker, Sep 22 2018
EXAMPLE
All solutions for n=4:
..0..3....0..1....0..1....0..3....0..1....0..3
..1..2....3..2....3..2....1..2....3..2....1..2
..0..1....0..3....1..0....0..3....0..1....3..0
..3..2....1..2....2..3....1..2....3..2....2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 30 2013
STATUS
approved