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A234353 Number of non-equivalent (mod D_3) ways to arrange 5 indistinguishable points on a triangular grid of side n so that no three points are collinear. 4
8, 140, 1290, 7374, 32477, 116420, 358112, 976063, 2425756, 5560046, 11946923, 24274195, 46975815, 87140153 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,1

COMMENTS

Column 5 of triangle A234350.

Without the restriction "non-equivalent (mod D_3)" the numbers are given by A194133.

LINKS

Table of n, a(n) for n=4..17.

EXAMPLE

There are a(4) = 8 non-equivalent ways to arrange 5 indistinguishable points (x) on a triangular grid of side 4. Some examples:

      x          x         .          .          .

     x x        . .       x .        x x        x .

    . . .      x . x     x . x      . x .      x . x

   . x x .    . x x .   . x x .    x . . x    . x . x

CROSSREFS

Cf. A234350, A194133

Arranging 3 points: A234351

Arranging 4 points: A234352

Arranging 6 points: A234354

Sequence in context: A201094 A061996 A345650 * A212442 A185248 A228867

Adjacent sequences:  A234350 A234351 A234352 * A234354 A234355 A234356

KEYWORD

nonn,more

AUTHOR

Heinrich Ludwig, Dec 30 2013

EXTENSIONS

a(14)-a(17) from Heinrich Ludwig, Apr 19 2016

STATUS

approved

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Last modified October 25 11:14 EDT 2021. Contains 348247 sequences. (Running on oeis4.)