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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

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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