Random number generator with 3 inputs

I am looking for a random number generator with 3 inputs for a terrain generator. The inputs are an x, y (position) and a seed value. And the function returns back a random number from 0-1.

So far I found this question, but this has 2 inputs. Although I can combine x and y to a single number, to get two inputs, this will restrict the choices I will have for x, y as they need to be sufficiently large (the terrain is infinite).

Is there any random function that takes in 3 inputs, or would I need to end up using the 2 input version?