[math-fun] superstring theory solves math problems?

http://www.ams.org/journals/bull/2000-37-04/S0273-0979-00-00875-2/S0273-0979... describes a remarkable conjectured formula (arising from generating functions ad series reversions) for the number of rational curves of degree d on a generic "quintic threefold." The formula gives the right answers for the first 9 cases. However, it is not even clear that the numbers it outputs, are always integers, although hundreds have been computed and always came out integer.