A212938 Number of n X 3 0..2 arrays with no column j greater than or equal to than column j-1 in all rows.

1, 181, 9019, 331489, 10669771, 320396041, 9245913139, 260489615329, 7229878904251, 198760197641401, 5430623746397059, 147781972534146769, 4010919223287633931, 108669462396348197161, 2940820425317878781779

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

Cf. A212943.

Sequence in context: A293655 A008379 A262141 * A070250 A226714 A083979

Adjacent sequences: A212935 A212936 A212937 * A212939 A212940 A212941

Keyword

nonn

Author

R. H. Hardin, May 31 2012

Status

approved