A239572 - OEIS

A239572

Triangle T(n, k) = Numbers of non-equivalent (mod D_3) ways to place k points on a triangular grid of side n so that no two of them are adjacent. Triangle read by rows.

1, 1, 2, 2, 1, 3, 6, 6, 1, 4, 16, 32, 24, 7, 1, 5, 32, 113, 200, 176, 66, 6, 7, 60, 329, 1053, 1976, 2096, 1162, 302, 34, 2, 8, 100, 790, 3932, 12565, 25676, 32963, 25638, 11294, 2493, 222, 7, 10, 160, 1702, 11988, 57275, 187984, 425329, 658608, 684671, 462519

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OFFSET

1,3

COMMENTS

Triangle T(n, k) is irregularly shaped: 1 <= k <= A239438(n). First row corresponds to n = 1.

The maximal number of points that can be placed on a triangular grid of side n so that no two of them are adjacent is given by A239438(n).

Without the restriction "non-equivalent (mod D_3)" numbers are given by A239567.

LINKS

Heinrich Ludwig, Table of n, a(n) for n = 1..136

EXAMPLE

Triangle begins

2, 2, 1;