OFFSET
1,1
COMMENTS
Row 3 of A201873.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) +2*a(n-3) -2*a(n-4) -a(n-6) +a(n-7).
Empirical g.f.: x*(3 + 2*x + x^2)*(1 + 3*x^2 - 2*x^3 + x^4) / ((1 - x)^3*(1 + x + x^2)^2). - Colin Barker, Feb 15 2018
EXAMPLE
Some solutions for n=12:
.-2....8...-2...-9....2..-10....9....1....0...-5...-3....5...-6...11....3....2
..3...-4....0....1...-3....1....0....1...-3....4....0...-2....0...-1....4...-2
.-1...-4....2....8....1....9...-9...-2....3....1....3...-3....6..-10...-7....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 06 2011
STATUS
approved