OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 2*a(n-2) + a(n-3) - a(n-5) - 3*a(n-6) + a(n-7).
Empirical g.f.: x*(1 + x - 2*x^2 - 5*x^3 - x^4 - 5*x^5 + 3*x^6) / ((1 - x)*(1 - 2*x^2 - 3*x^3 - 3*x^4 - 2*x^5 + x^6)). - Colin Barker, Jan 09 2019
EXAMPLE
Some solutions for n=7:
..1..3..1..1....1..3..1..1....1..3..1..1....1..2..2..1....1..3..1..1
..1..1..3..1....1..1..3..1....1..1..4..2....1..1..1..1....1..1..3..1
..1..3..1..1....1..3..1..1....1..3..3..1....1..3..3..1....1..3..1..1
..1..1..4..2....1..1..3..2....1..1..1..1....1..1..1..1....1..1..4..2
..1..3..3..1....1..3..4..1....1..3..3..1....1..3..3..1....1..3..3..1
..1..1..1..1....1..1..1..1....1..1..1..1....1..1..1..1....2..4..1..1
..1..2..2..1....1..2..2..1....1..2..2..1....1..2..2..1....1..1..3..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 19 2015
STATUS
approved