A234349 Maximal number of points that can be placed on a triangular grid of side n so that no three points are collinear.

1, 3, 4, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 19, 20, 22, 23, 24, 25, 27, 28

Offset: 1

Author

Heinrich Ludwig, Dec 24 2013

Keywords

• nonn
• hard
• more

Comments

Length of the n-th row in triangle A194136 and triangle A234350.

Differs from A007401 first at n=14.

Examples

			In a triangular grid of side 5 at most 7 points (x) can be placed so that no three of them are on a straight line. (There are exactly 2 ways to do it, rotations and reflections ignored.)
        .              x
       . x            . .
      x . x          x . x
     x . x .        . x x .
    . x . x .      . x . x .
		

Crossrefs

Cf. A194136, A234350.

Extensions

a(13)-a(14) from Heinrich Ludwig, Jan 10 2014

a(15)-a(16) from Heinrich Ludwig, Jan 28 2014

a(17)-a(21) from Rob Pratt, Jul 27 2015