For n ≤ 27 we present exact values for the maximum number h(n) of halving lines and eh(n) of halving pseudolines, determined by n points in the plane. For this range of values of n we also present exact values of the rectilinear cr(n) and the pseudolinear e cr(n) crossing number of the complete graph Kn. eh(n) and e cr(n) are new for n ∈ {14, 16, 18, 20, 22, 23, 24, 25, 26, 27}, h(n) is new for...