OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = -a(n-1) + 3*a(n-3) + 3*a(n-4) - 2*a(n-6) - 2*a(n-7) for n>9.
Empirical g.f.: x*(111 + 213*x + 221*x^2 - 79*x^3 - 357*x^4 - 325*x^5 - 138*x^6 + 42*x^7 + 2*x^8) / ((1 - x)*(1 + x)*(1 + x + x^2)*(1 - 2*x^3)). - Colin Barker, Dec 06 2018
EXAMPLE
Some solutions for n=4:
..0..1..0..0..1..0....0..1..0..0..1..0....0..1..0..0..2..0....0..1..0..0..2..0
..2..2..0..2..2..0....0..0..1..0..0..2....3..3..0..3..3..0....3..3..0..3..3..0
..1..0..0..1..0..0....0..3..3..0..3..3....2..0..0..1..0..0....1..0..0..1..0..0
..0..1..0..0..1..0....0..1..0..0..1..0....0..2..0..0..1..0....0..1..0..0..1..0
..2..2..0..2..2..0....0..0..1..0..0..1....3..3..0..3..3..0....3..3..0..3..3..0
..1..0..0..1..0..0....0..2..2..0..2..2....1..0..0..2..0..0....1..0..0..1..0..0
..0..1..0..0..1..0....0..1..0..0..1..0....0..1..0..0..2..0....0..2..0..0..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 20 2014
STATUS
approved