OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 4*a(n-3) - 4*a(n-4).
Empirical g.f.: x*(29 + 16*x + 24*x^2 - 84*x^3) / ((1 - x)*(1 - 4*x^3)). - Colin Barker, Nov 08 2018
EXAMPLE
Some solutions for n=6:
..1....2....2....2....0....4....1....2....1....2....4....0....2....4....0....2
..3....4....3....1....4....0....0....4....3....4....3....2....0....2....1....4
..2....3....1....3....2....2....2....3....2....0....2....4....4....0....2....0
..1....2....2....2....0....1....4....2....1....2....1....3....2....4....0....2
..0....4....0....1....4....3....3....1....3....4....0....2....3....2....4....1
..2....0....4....0....2....2....2....0....2....3....2....1....4....0....2....3
..4....2....2....2....0....1....4....2....1....2....1....3....2....4....0....2
..3....4....0....1....4....3....3....1....0....1....3....2....3....2....1....1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 06 2014
STATUS
approved