OFFSET
1,1
COMMENTS
Column 1 of A206255.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) +12*a(n-2) -27*a(n-3).
a(n) = A006139(n+2)^2.
Conjectures from Colin Barker, Jun 14 2018: (Start)
G.f.: x*(49 + 165*x - 432*x^2) / ((1 + 3*x)*(1 - 7*x + 9*x^2)).
a(n) = 2^(-n)*((-1)^n*2^(1+n)*3^(3+n) + (77-20*sqrt(13))*(7-sqrt(13))^n + (7+sqrt(13))^n*(77+20*sqrt(13))) / 13.
(End)
EXAMPLE
Some solutions for n=4:
..1..0....2..1....2..1....2..3....2..3....3..3....3..3....0..3....0..3....0..1
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..2....0..2....0..0
..0..3....1..0....2..1....2..3....0..0....1..1....3..1....0..3....0..0....0..1
..0..1....2..0....0..0....0..0....0..0....0..0....0..0....0..2....3..3....0..2
..0..3....1..0....3..0....1..3....3..0....1..1....0..1....0..1....0..0....0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 05 2012
STATUS
approved