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) - a(n-6) + a(n-7) for n>9.
Empirical g.f.: x*(463 - 161*x - 23*x^2 - 1371*x^3 + 513*x^4 + 108*x^5 + 457*x^6 - 173*x^7 - 38*x^8) / ((1 - x)*(1 - 3*x^3 + x^6)). - Colin Barker, Dec 02 2018
EXAMPLE
Some solutions for n=4:
..3..0..1..0..1..0..1....2..2..0..2..2..0..2....0..2..2..0..2..2..0
..3..1..0..1..0..1..0....3..0..1..0..3..1..0....2..3..3..2..3..3..2
..3..0..1..0..1..0..1....3..0..1..0..3..1..0....2..3..3..2..3..3..2
..3..1..0..1..0..1..0....2..2..0..2..2..0..2....0..2..2..0..2..2..0
..3..0..1..0..1..0..1....3..0..1..0..3..1..0....2..3..3..2..3..3..2
..3..1..0..1..0..1..0....3..0..1..0..3..1..0....2..3..3..2..3..3..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 16 2014
STATUS
approved