OFFSET
1,1
COMMENTS
Column 2 of A223297.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 9*a(n-1) - 6*a(n-2).
Conjectures from Colin Barker, Aug 19 2018: (Start)
G.f.: 24*x*(1 - 2*x) / (1 - 9*x + 6*x^2).
a(n) = (2^(2-n)*((9-sqrt(57))^n*(3+sqrt(57)) + (-3+sqrt(57))*(9+sqrt(57))^n)) / sqrt(57).
(End)
EXAMPLE
Some solutions for n=3:
..2..0....0..3....6..0....4..0....3..0....0..3....0..1....4..0....8..0....0..2
..0..1....3..0....0..3....0..4....0..5....6..0....8..0....0..6....0..3....2..0
..7..0....0..6....8..0....4..3....1..0....0..6....7..8....3..0....8..0....0..6
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 19 2013
STATUS
approved