A182192 Number of lower triangular n X n arrays colored with integers 0 upwards introduced in row major order, with no element equal to any horizontal or vertical neighbor

1, 2, 42, 12840, 87852626, 18383354944364, 152834703739877723176

Offset

1,2

Links

Table of n, a(n) for n=1..7.

Example

Some solutions for n=4
..0........0........0........0........0........0........0........0
..1.2......1.0......1.0......1.2......1.2......1.2......1.2......1.0
..2.1.3....2.3.0....0.2.1....2.0.3....3.1.4....2.0.3....2.3.4....2.3.4
..1.2.1.2..3.0.4.5..1.3.0.3..1.4.1.0..5.4.2.3..4.2.5.4..5.0.3.4..1.5.2.6

Crossrefs

Sequence in context: A193271 A193272 A193273 * A330229 A039622 A130506

Adjacent sequences: A182189 A182190 A182191 * A182193 A182194 A182195

Keyword

nonn

Author

R. H. Hardin Apr 23 2012

Status

approved