OFFSET
1,1
COMMENTS
Row 1 of A206169.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 18*a(n-1) - 101*a(n-2) + 192*a(n-3) - 108*a(n-4).
Conjectures from Colin Barker, Mar 04 2018: (Start)
G.f.: x*(15 - 185*x + 626*x^2 - 576*x^3) / ((1 - x)*(1 - 2*x)*(1 - 6*x)*(1 - 9*x)).
a(n) = (9 + 3*2^n + 2^(1+n)*3^n + 2*9^n) / 3.
(End)
EXAMPLE
Some solutions for n=4:
..0..0..1..0..2....0..0..0..0..1....0..0..0..1..2....0..1..2..3..2
..3..2..1..3..3....1..1..1..2..1....0..1..0..0..1....3..1..2..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 04 2012
STATUS
approved