A211925 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)/2-3

0, 2, 23, 340, 2577, 12616, 46582, 141478, 372360, 878257, 1899356, 3828287, 7278658, 13174305, 22863037, 38258971, 62017867, 97750188, 150276925, 225933542, 332927711, 481756822, 685691568

Offset

1,2

Comments

Column 2 of A211930

Links

Table of n, a(n) for n=1..23.

Formula

Empirical: a(n) = (1/128)*n^8 + (1/32)*n^7 - (41/192)*n^6 - (1/4)*n^5 + (345/128)*n^4 - (367/96)*n^3 - (143/96)*n^2 + (169/24)*n - 3 for n>1

Example

Some solutions for n=4
..0........0........0........0........0........0........0........0
..1.2......1.2......1.2......1.2......1.0......1.2......1.2......1.2
..3.1.4....3.4.5....3.4.2....3.4.5....2.3.4....3.4.5....3.1.4....3.4.2
..5.6.1.7..6.2.7.6..5.0.6.7..2.6.7.8..5.6.0.7..6.2.7.4..5.6.7.2..5.3.6.7

Crossrefs

Sequence in context: A216549 A091693 A276025 * A277830 A197740 A234868

Adjacent sequences: A211922 A211923 A211924 * A211926 A211927 A211928

Keyword

nonn

Author

R. H. Hardin Apr 25 2012

Status

approved