In a CS course I'm taking there is an example of a language that is not regular:
{a^nb^n | n >= 0}
I can understand that it is not regular since no Finite State Automaton/Machine can be written that validates and accepts this input since it lacks a memory component. (Please correct me if I'm wrong)
The wikipedia entry on Regular Language also lists this example, but does not provide a (mathematical) proof why it is not regular.
Can anyone enlighten me on this and provide proof for this, or point me too a good resource?