Cap set
In affine geometry, a cap set is a subset of (an -dimensional affine space over a three-element field) with no three elements in a line.The cap set problem is the problem of finding the size of the largest possible cap set, as a function of . The first few cap set sizes are 1, 2, 4, 9, 20, 45, 112, ... (sequence in the OEIS). Cap sets may be defined more generally as subsets of finite affine or projective spaces with no three in line, where these objects are simply called caps. The "cap set" terminology should be distinguished from other unrelated mathematical objects with the same name, and in particular from sets with the compact absorption property in function spaces as well as from compact convex co-convex subsets of a convex set. (Wikipedia).
