A211928 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, vertical or antidiagonal neighbor, and containing the value n(n+1)/2-6.

0, 0, 27, 5809, 2484024, 249499909, 9339489832, 186659686448

Offset

1,3

Comments

Column 5 of A211930.

Links

Table of n, a(n) for n=1..8.

Example

Some solutions for n=4
..0........0........0........0........0........0........0........0
..1.0......1.2......1.2......1.2......1.0......1.2......1.0......1.2
..2.3.4....3.0.2....3.0.4....3.4.3....2.3.0....0.1.3....2.3.0....3.1.0
..5.0.5.1..4.3.5.6..1.5.3.0..1.2.1.3..0.4.3.5..3.4.0.3..4.5.6.0..4.2.1.2

Crossrefs

Cf. A211930.

Sequence in context: A278686 A046367 A059795 * A123395 A051680 A013828

Adjacent sequences: A211925 A211926 A211927 * A211929 A211930 A211931

Keyword

nonn,changed

Author

R. H. Hardin, Apr 25 2012

Status

approved