@user2180, at the time of this message, the question
math.stackexchange.com/questions/2594578/… has been undeleted. I cast one delete vote (couldn't resist) and have flagged to post to mods, and contacted both quid and Daniel F, so they can delete with a final delete. Period. It might not hurt to flag the question, in the meantime, re the post being deleted once and for all.