Tessellate the plane into rows of hexagons. Consider a subset of
rows of these hexagons,
each row containing
hexagons, forming a rhombus-shaped chessboard of
spaces. Two kings placed on the board are said to “attack” each other if
their spaces share a side or corner. Placing kings in alternating spaces
of every other row results in an arrangement where no two of the
kings
are attacking each other. According to our specific distance metric,
is in fact the largest number of kings that can be placed on such a board
with no two kings attacking one another, for a maximum “density” of
. We consider a
generalization of this maximum density problem, instead requiring that no king attacks more
than other kings
for
. For instance
when
the density
is at most
.
For each
we give constructive lower bounds on the density, and use systems of inequalities and
discharging arguments to yield upper bounds, where the bounds match in most
cases.
Keywords
$k$-dependence, combinatorial chessboard, optimization,
discharging, linear programming