OFFSET
1,1
COMMENTS
Column 3 of A209374.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) +5*a(n-3) +2*a(n-4) +6*a(n-5) +5*a(n-6) -2*a(n-8) -a(n-9) for n>12.
Empirical g.f.: x*(19 + 46*x - 53*x^2 - 83*x^3 - 252*x^4 - 315*x^5 - 423*x^6 - 476*x^7 - 163*x^8 + 111*x^9 + 122*x^10 + 35*x^11) / ((1 - 2*x - 2*x^2 - x^3)*(1 + 2*x^2 + 2*x^4 - x^6)). - Colin Barker, Feb 18 2018
EXAMPLE
Some solutions for n=5:
..2..2..3....3..2..3....3..2..3....1..2..1....2..3..1....1..2..1....3..1..3
..1..3..1....1..2..1....1..2..1....3..1..3....2..1..3....3..1..3....1..3..2
..3..1..2....3..1..3....3..1..3....2..3..1....1..3..2....1..3..2....3..1..3
..1..3..1....1..3..1....1..3..1....2..1..3....3..1..3....3..1..2....2..2..1
..3..2..3....2..2..3....2..1..3....1..3..1....2..2..1....2..3..1....3..1..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 07 2012
STATUS
approved