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A234351
Number of non-equivalent (mod D_3) ways to arrange 3 indistinguishable points on a triangular grid of side n so that no three points are collinear.
4
1, 5, 22, 77, 217, 530, 1149, 2288, 4231, 7400, 12322, 19725, 30486, 45768, 66917, 95669
OFFSET
2,2
COMMENTS
Column 3 of triangle A234350.
Without the restriction "non-equivalent (mod D_3)" the numbers are given by A194131.
EXAMPLE
There are a(3) = 5 non-equivalent ways to arrange 3 indistinguishable points (x) on a triangular grid of side 3:
x . x x x
. . x x x x . . x .
x . x . x . . . . . x x . x .
CROSSREFS
Arranging 4 points: A234352
Arranging 5 points: A234353
Arranging 6 points: A234354
Sequence in context: A338707 A058750 A058752 * A255802 A266358 A183925
KEYWORD
nonn,more
AUTHOR
Heinrich Ludwig, Dec 30 2013
EXTENSIONS
a(14)-a(17) from Heinrich Ludwig, Apr 19 2016
STATUS
approved