OFFSET
1,2
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) + 3*a(n-5) + 3*a(n-6) - 2*a(n-8) - a(n-9).
Empirical g.f.: x*(1 + 2*x + 6*x^2 + 6*x^3 + 6*x^4 + 3*x^5 - 2*x^6 - 3*x^7 - x^8) / ((1 + x^2 - x^3)*(1 + x^2 + x^3)*(1 - x - 2*x^2 - x^3)). - Colin Barker, Jan 07 2019
EXAMPLE
Some solutions for n=4:
..7..8..0..3..4....0..1..2..3..4....0..8..9..3..4....0..8..2..3..4
..5..1..2..6..9....5..6..7..8..9....5..1..2..6..7....5..1..7..6..9
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 12 2015
STATUS
approved