OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 5*a(n-1) - 6*a(n-2) for n>5.
Conjectures from Colin Barker, Sep 10 2018: (Start)
G.f.: x*(17 + 58*x + 8*x^2 - 188*x^3 - 264*x^4) / ((1 - 2*x)*(1 - 3*x)).
a(n) = 3^(3+n) - 2^(3+n) for n>3.
(End)
EXAMPLE
Some solutions for n=4:
.-7...-4....3....4....3....1....1...-7....3....1....4...-3...-4...-2...-7...-1
..7....2....0...-6...-3....3....2....6....3....2...-2....4....0....3....7....2
.-4....2...-3....5....0...-5...-1...-1...-6...-4...-2...-3....3...-2...-3....0
..2...-4....3...-3....3....7...-1...-1....4....4....3....0...-4...-2...-2...-1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 19 2013
STATUS
approved