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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. 9
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 (list; graph; refs; listen; history; text; internal format)
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

  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;

CROSSREFS

Cf. A239438, A239567.

Column 1 is A001399,

Column 2 is A032091,

Column 3 is A239573,

Column 4 is A239574,

Column 5 is A239575,

Column 6 is A279446.

Sequence in context: A163649 A110858 A008279 * A056043 A187005 A158497

Adjacent sequences:  A239569 A239570 A239571 * A239573 A239574 A239575

KEYWORD

nonn,tabf

AUTHOR

Heinrich Ludwig, Mar 22 2014

STATUS

approved

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Last modified November 15 11:18 EST 2019. Contains 329144 sequences. (Running on oeis4.)