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[Vi Hart](http://vihart.com) has a fantastic collection of videos about doodling based on mathematical concepts. The one I am showing here involves doodling based on graph theory — those who know graph theory’s origins in the classical problem of [“The Seven Bridges of Konigsberg”](http://en.wikipedia.org/wiki/Seven_Bridges_of_Königsberg) will recognize the early doodles as being terrific examples of Euler’s work. Enjoy! I am showing all of them to my six year old.