A234349 - OEIS

%I #20 Jul 27 2015 13:27:24

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

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

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

%C Differs from A007401 first at n=14.

%e 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.)

%e         .              x

%e        . x            . .

%e       x . x          x . x

%e      x . x .        . x x .

%e     . x . x .      . x . x .

%Y Cf. A194136, A234350.

%K nonn,hard,more

%O 1,2

%A _Heinrich Ludwig_, Dec 24 2013

%E a(13)-a(14) from _Heinrich Ludwig_, Jan 10 2014

%E a(15)-a(16) from _Heinrich Ludwig_, Jan 28 2014

%E a(17)-a(21) from _Rob Pratt_, Jul 27 2015