OFFSET
1,2
COMMENTS
Column 3 of A212943.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 55*a(n-1) - 936*a(n-2) + 4860*a(n-3).
a(n) = 10^n - 2*18^n + 27^n. - Vaclav Kotesovec, May 31 2012
Empirical g.f.: x*(1 + 126*x) / ((1 - 10*x)*(1 - 18*x)*(1 - 27*x)). - Colin Barker, Jul 21 2018
EXAMPLE
Some solutions for n=4:
..2..1..2....2..2..0....0..0..0....1..0..1....0..1..1....0..1..2....1..1..1
..0..2..2....2..1..1....2..1..0....2..0..2....2..2..2....0..1..0....2..1..1
..2..0..0....1..1..0....0..2..0....0..2..2....1..2..2....0..2..1....1..1..1
..2..1..0....0..1..2....0..0..2....2..1..0....2..1..0....1..0..0....0..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 31 2012
STATUS
approved