derivation of Hartley function
We want to show that the Hartley function is the onlyfunction mapping natural numbers to real numbers that
- 1.
(),
- 2.
(monotonicity), and
- 3.
(normalization).
Let be a function on positive integers that satisfies the above three properties. Using the additive property, it is easy to see that the value of must be zero. So we want to show that for all integers .
From the additive property, we can show that for any integer and ,
(1) |
Let be an integer. Let be any positive integer. There is a uniqueinteger determined by
Therefore,
and
On the other hand, by monotonicity,
Using Equation (1) and , we get
and
Hence,
Since can be arbitrarily large, the difference on the lefthand of the above inequality must be zero,