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

1,2

Comments

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

Differs from A007401 first at n=14.

Links

Table of n, a(n) for n=1..21.

Example

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.

Sequence in context: A143344 A007401 A275481 * A042954 A361457 A247987

Adjacent sequences: A234346 A234347 A234348 * A234350 A234351 A234352

Keyword

nonn,hard,more

Author

Heinrich Ludwig, Dec 24 2013

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

Status

approved