Let's begin with the case a=b, this time using values 1, 2, 3, 4, and 5:

Again, I will conjecture that the next two cases should be ellipses. Let's see:

a<b, for values 1, 2, 3, 4, 5, and 6:

a>b, for values 1, 2, 3, 4, 5, and 6: