TITLE: Recreational mathematical papers
QUESTION [8 upvotes]: Sometimes it is nice to get a less technical paper on mathematics to read and learn something different for a change. These papers often make us discover some new curiosity, to think about the process of learning mathematics or even about mathematics itself and this could be a really nice way to quickly 'scape' our daily problems to amuse ourselves with what I will call here recreational mathematics. As an example, I could mention this paper discussing our unability of seeing beyond three dimensions, which is something really curious. What are other interesting recreational mathematical papers to read during our break time?
Note: Maybe the term 'recreational' fits better when applied to puzzles or something like this but I didn't know what else to call it.

REPLY [7 votes]: Two of my favorite recreational papers are:
J-F Mestre, R Schoof, L Washington and D Zagier, 
Quotients homophones des groupes libres. Homophonic quotients of free groups
Experiment. Math. 2 (1993), no. 3, 153–155.
Norman Wildberger, Real fish, real numbers, real jobs, The Mathematical Intelligencer 21(2), (June 1999), 4-7. Here is a youtube recording of the author reading this paper.
In fact the Intelligencer and the American math monthly have many papers of this type. Also a mainstream mathematical journal St Peterburg Mathematical Journal has a permanent department "Easy reading for professionals".