A212022 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, diagonal or antidiagonal neighbor, and containing the value n(n+1)/2-3

0, 2, 25, 346, 2589, 12636, 46612, 141520, 372416, 878329, 1899446, 3828397, 7278790, 13174461, 22863219, 38259181, 62018107, 97750460, 150277231, 225933884, 332928091, 481757242, 685692030

Offset

1,2

Comments

Column 2 of A212026

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 - (47/96)*n^2 + (97/24)*n - 1 for n>1

Example

Some solutions for n=4
..0........0........0........0........0........0........0........0
..0.1......1.2......1.2......0.1......1.2......1.2......0.1......1.2
..2.1.3....3.4.5....3.4.5....2.3.4....3.4.5....1.3.4....2.3.4....3.4.5
..4.5.6.7..6.7.2.0..0.6.1.7..5.1.6.7..0.6.7.1..5.6.7.5..5.0.6.7..6.2.7.4

Crossrefs

Sequence in context: A085830 A270346 A367506 * A198710 A074209 A209467

Adjacent sequences: A212019 A212020 A212021 * A212023 A212024 A212025

Keyword

nonn

Author

R. H. Hardin Apr 26 2012

Status

approved