An excellent, simple extension to this is to throw simple arithmetic operators into the mix (digits 0-9, +, -, / and * perhaps) and to try and breed an algorith

An excellent, simple extension to this is to throw simple arithmetic operators into the mix (digits 0-9, +, -, / and * perhaps) and to try and breed an algorithm which when evaluated yields a number, like the number 500. You can get startlingly close answers and interesting equations this way.