In
combinatorics, a
thrackle is a
graph formed by a
collection of
curves in the
plane, with the
property that the
curves
corresponding to any
pair of
edges
meet in a
single point, which is either an
endpoint of both
edges or a place where the two
curves
cross. Every
planar straight line graph
thrackle has at most as many
edges as
vertices;
Conway's thrackle conjecture states that this is true even for
curved
thrackles. A
thrackle also happens to be one of the
coolest sounding
things in
mathematics,
IMHO :0)
--back to
combinatorics--