OFFSET
1,1
COMMENTS
Column 3 of A212930.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 37*a(n-1) -279*a(n-2) +243*a(n-3).
Explicit formula: a(n) = 27^n - 2*9^n + 1. - Vaclav Kotesovec, May 31 2012
Empirical g.f.: 2*x*(5 + 99*x) / ((1 - x)*(1 - 9*x)*(1 - 27*x)). - Colin Barker, Jul 21 2018
EXAMPLE
Some solutions for n=3:
..2..2..2....0..1..1....1..2..1....1..0..1....0..0..0....2..1..2....2..1..0
..0..0..2....0..0..2....2..1..2....1..2..2....1..2..0....1..2..2....2..1..2
..1..2..0....0..0..2....1..0..2....2..1..2....1..2..2....1..2..0....2..1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 31 2012
STATUS
approved