OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) - 8*a(n-3) - 4*a(n-4).
Empirical g.f.: 4*x^2*(1 - x)^2 / (1 - 2*x - 2*x^2)^2. - Colin Barker, Sep 18 2018
EXAMPLE
Some solutions for n=4:
..0..1..2..0....0..1..0..0....0..1..0..2....0..1..0..2....0..1..0..1
..0..1..0..1....2..1..2..1....2..1..2..1....1..2..0..1....1..2..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 25 2013
STATUS
approved