OFFSET
1,2
COMMENTS
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
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