Horner on P(x) = 2x^3 - 6x^2 + 2x - 1 at x = 3
  i = 3   p = A[3] + 3 * (previous p) = 2
  i = 2   p = A[2] + 3 * (previous p) = 0
  i = 1   p = A[1] + 3 * (previous p) = 2
  i = 0   p = A[0] + 3 * (previous p) = 5
Horner: P(3) = 5 using 4 multiplications
Naive : P(3) = 5 using 10 multiplications

 degree n   Horner mults   naive mults
        3              4            10
       10             11            66
      100            101          5151
     1000           1001        501501
