A201620 Number of nX3 0..3 arrays with rows and columns lexicographically nondecreasing and every element equal to at least one horizontal or vertical neighbor

4, 56, 378, 3699, 31802, 256836, 1877283, 12466658, 75830797, 426330762, 2234037739, 10991599638, 51096736814, 225648517165, 951032245643, 3840801817887, 14914920467311, 55860582248737, 202312954584987

Offset

1,1

Comments

Column 3 of A201625

Links

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

Formula

Empirical: a(n) is a polynomial of degree 63 for n>35

Example

Some solutions for n=5
..0..0..1....0..0..2....0..0..1....0..1..1....0..0..0....0..2..3....0..0..1
..0..0..1....0..0..2....0..0..1....0..1..1....0..3..3....0..2..3....0..0..1
..0..1..3....1..1..2....0..1..1....3..1..2....1..0..0....1..1..0....2..2..2
..0..1..3....3..3..0....3..1..3....3..2..2....1..3..3....3..0..0....2..3..3
..0..2..2....3..3..0....3..3..3....3..3..2....2..2..2....3..1..1....3..3..3

Crossrefs

Sequence in context: A201448 A195577 A255011 * A204108 A077122 A020540

Adjacent sequences: A201617 A201618 A201619 * A201621 A201622 A201623

Keyword

nonn

Author

R. H. Hardin Dec 03 2011

Status

approved