A211908 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, and containing the value n(n+1)/2-5.

0, 0, 42, 6927, 605769, 18239150, 281228042, 2788818593, 20221781939

Offset

1,3

Comments

Column 4 of A211910.

Links

Table of n, a(n) for n=1..9.

Example

Some solutions for n=4
..0........0........0........0........0........0........0........0
..1.2......1.2......1.2......1.2......1.2......1.2......1.2......1.2
..3.4.5....3.1.4....2.0.3....3.4.1....0.3.4....3.4.3....3.4.5....2.3.4
..4.5.6.2..5.6.1.4..4.1.5.3..2.5.6.4..1.5.6.3..5.3.0.4..5.1.3.4..3.4.5.6

Crossrefs

Cf. A211910.

Sequence in context: A167668 A277665 A215837 * A246621 A153471 A006699

Adjacent sequences: A211905 A211906 A211907 * A211909 A211910 A211911

Keyword

nonn

Author

R. H. Hardin, Apr 25 2012

Status

approved