My bad, I guess. I thought the OP just wanted an ID on the joke about mathematicians and engineers, which in itself isn't sci-fi or fantasy at all, although readily identifiable as part of "scientist folk humour" in one form or another. Had I realised that what he was really looking for was a sci-fi short story featuring this joke, I wouldn't have migrated it.
The reason for my speed in migrating it was partly because I happened to see it quickly, but mostly because I wanted to spare the OP downvotes for posting an off-topic question here (something which often happens even if the question is of good quality disregarding scope considerations).