OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-2) + 10*a(n-3) - a(n-4) - 5*a(n-5) - 15*a(n-6) + a(n-7) + 4*a(n-8) + 2*a(n-9) + 10*a(n-10) + 5*a(n-11) - 6*a(n-13).
Empirical g.f.: x*(1 + 3*x + 4*x^2 - x^4 + 4*x^6 - 4*x^7 - 6*x^8 + 6*x^9 + 6*x^10 - 4*x^12) / (1 - 2*x^2 - 10*x^3 + x^4 + 5*x^5 + 15*x^6 - x^7 - 4*x^8 - 2*x^9 - 10*x^10 - 5*x^11 + 6*x^13). - Colin Barker, Oct 26 2018
EXAMPLE
Some solutions for n=4:
..3..0....3..0....3..0....3..0....3..0....3..0....3..0....3..0....3..0....3..0
..2..1....2..1....2..1....2..3....2..1....3..1....3..1....3..1....2..1....2..1
..2..1....2..0....2..0....2..0....2..1....2..1....3..2....3..1....2..1....2..0
..3..2....3..1....3..0....3..2....3..1....3..1....2..3....2..1....2..1....3..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 30 2014
STATUS
approved