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A234352
Number of non-equivalent (mod D_3) ways to arrange 4 indistinguishable points on a triangular grid of side n so that no three points are collinear.
4
2, 24, 153, 713, 2557, 7661, 20055, 47153, 101821, 205322, 390580, 707708, 1229969, 2060777, 3344487
OFFSET
3,1
COMMENTS
Column 4 of triangle A234350.
Without the restriction "non-equivalent (mod D_3)" the numbers are given by A194132.
EXAMPLE
There are a(3) = 2 non-equivalent ways to arrange 4 indistinguishable points (x) on a triangular grid of side 3:
x .
x x x x
. x . x . x
CROSSREFS
Arranging 3 points: A234351
Arranging 5 points: A234353
Arranging 6 points: A234354
Sequence in context: A163752 A035600 A189247 * A241623 A288443 A108476
KEYWORD
nonn,more
AUTHOR
Heinrich Ludwig, Dec 30 2013
EXTENSIONS
a(14)-a(17) from Heinrich Ludwig, Apr 19 2016
STATUS
approved