Unfortunately foor the mathematicians, that doesn't work. But it is a good example illustrating the difference between arbitrarily large and infinite. You are right that the mathematicians can choose a number N, and let each representative sequence begin with (1, 2, 3, ..., N). And you are right that there is no finite limit to how large N can be. They can make N arbitrarily large. But perhaps surprisingly, that doesn't mean they can go on like that infinitely. They still must choose a number N, and there are no infinite numbers. In terms of sequences, infinity means forever. And forever means the sequence can't change at some point to match another sequence. There is only one sequence which goes x1=1, x2=2, x3=3, and so on for infinitely many terms.
As for the mathematicians, the unfortunate part is that no matter how large they make N, the probability is still 0 that their sequence matches its representative sequence at the N-th place. No matter how large they make N, it will still be infinitely small compared to the concept of infinity. (引用終り)
