What @cAtte basically suggests is what I described here for another use case, but with some general advice too:
In this case, tip 1. (“you need to store the data somewhere before creating the table”) is the important one; tip 2. not so much in this particular instance (“you need to make sure that you operate on numbers and not content”). The reason is that you don’t want to edit existing data, but insert automatically generated data alongside the existing one.