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.

8, 140, 1290, 7374, 32477, 116420, 358112, 976063, 2425756, 5560046, 11946923, 24274195, 46975815, 87140153

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: A061996 A345650 A092703 * 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