OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) + 20*a(n-3) + 25*a(n-4).
Empirical g.f.: 16*x^2 / ((1 + x)*(1 - 5*x)*(1 + 5*x^2)). - Colin Barker, Sep 25 2018
EXAMPLE
Some solutions for n=2:
..0..1..0....0..0..0....0..2..0....0..3..0....0..0..0....0..3..0....0..2..0
..0..1..2....3..1..1....1..1..3....2..1..0....3..1..1....0..1..2....3..1..1
..2..3..0....0..2..2....2..0..0....0..1..2....2..2..0....0..1..2....0..0..2
..2..3..2....1..3..1....3..3..3....0..3..0....1..3..1....0..3..0....3..3..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 02 2013
STATUS
approved