OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-2) + 3*a(n-3) - 3*a(n-4) - 4*a(n-5) - 2*a(n-6) + 3*a(n-7) - a(n-9) + 2*a(n-11) - 2*a(n-12) + 2*a(n-15) for n>17.
Empirical g.f.: x*(2 + 3*x - 4*x^2 - 5*x^3 + 9*x^4 - x^5 - 16*x^6 - 12*x^7 - x^8 + 3*x^9 + 3*x^10 + 11*x^12 - 10*x^13 - 8*x^14 + 6*x^15 + 8*x^16) / ((1 - x)*(1 + x - 2*x^2 - 5*x^3 - 2*x^4 + 2*x^5 + 4*x^6 + x^7 + x^8 + 2*x^9 + 2*x^10 + 2*x^12 + 2*x^13 + 2*x^14)). - Colin Barker, Oct 29 2018
EXAMPLE
Some solutions for n=4:
..3..3..2..2....3..3..2..2....3..2..3..3....3..2..3..3....3..3..2..2
..2..1..1..3....2..2..0..0....2..1..1..0....2..1..1..2....2..2..0..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 15 2014
STATUS
approved