OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + 8*a(n-2) + 4*a(n-3).
Empirical g.f.: 4*x*(14 + 31*x + 14*x^2) / (1 - 2*x - 8*x^2 - 4*x^3). - Colin Barker, Oct 12 2018
EXAMPLE
Some solutions for n=5:
..1..0....1..0....2..3....1..3....2..3....2..3....2..1....3..1....4..2....1..3
..3..2....3..1....0..1....2..4....3..1....4..2....0..2....1..2....3..1....3..4
..1..3....1..2....2..0....3..2....4..3....3..4....2..1....3..4....2..0....1..3
..2..1....3..4....1..2....1..3....2..4....1..2....1..3....1..3....1..2....3..2
..0..2....1..2....3..4....2..4....1..3....3..4....3..2....2..1....3..1....2..4
..2..3....2..4....1..3....1..3....0..2....4..2....1..3....1..3....4..3....4..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 18 2013
STATUS
approved