Recursion, fractals, hexagons, etc
History of hexaflexagons, Konstfack student project by Anna Lundh:
http://annalundh.com/hexa_flexagon_f_ever/
Vi Hart: Doodling in Math
https://www.khanacademy.org/math/math-for-fun-and-...
Martin Gardner: Hexaflexagons and Other Mathematical Diversions
http://geofhagopian.net/papers/GARDNER01.pdf
Daniel Shiffman: Nature of Code
http://natureofcode.com/book/chapter-8-fractals/
