A212925 Number of n X 3 0..2 arrays with no column j greater than column j-1 in all rows.

10, 568, 18226, 518320, 14230810, 386357608, 10450787266, 282343443040, 7624822644010, 205884158525848, 5558997804436306, 150094070437926160, 4052550069287319610, 109418943377927449288, 2954312294768569509346

Offset: 1

Author

R. H. Hardin, May 31 2012

Keywords

• nonn

Comments

Column 3 of A212930.

Examples

			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
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Cf. A212930.

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