Creating a random integer from an array of integers

Is it possible to generate pseudo random integers from an integer array? I don't mean picking a random integer from an array, but instead doing something like

[1,2,3] = 4542

[56,89,42] = 80421

Finally, is it possible to have the output be completely random, instead of gradually changing? E.g. I would like this not this.

Thanks for any input.