OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + a(n-3) - 2*a(n-4) + 4*a(n-5) + a(n-6) - a(n-9).
Empirical g.f.: x*(1 + x - 2*x^2 + 3*x^3 - x^7) / ((1 - 2*x - x^3)*(1 + 2*x^4 - x^6)). - Colin Barker, Jan 08 2019
EXAMPLE
Some solutions for n=4:
..2..3....2..3....1..3....2..3....1..3....1..3....2..3....2..3....2..3....2..3
..0..1....4..5....4..5....0..5....0..5....0..5....4..1....0..1....0..1....4..1
..6..7....1..0....6..0....1..7....2..7....6..7....5..0....6..7....5..7....6..0
..8..5....8..9....8..2....8..9....8..9....8..2....8..9....8..9....8..9....8..9
..9..4....6..7....9..7....6..4....6..4....9..4....6..7....5..4....6..4....5..7
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 14 2015
STATUS
approved