SUMS: Poladian -- Gauss, the heptadecagon and the freemasons

This Thursday’s SUMS talk is being given by Leon Poladian.  

Abstract: How can modulo arithmetic help decide if certain polygons can be drawn using
only straight edge and compasses? Gauss showed how to do this construction when he was
19 years old.  He was so impressed that he wanted a heptadecagon inscribed on his
tombstone, but the stonemason said that it was not worth the effort since it would look
very much like a circle.  It does appear on an East German postage stamp from 1977 (and
it does look like a circle!).  Supposedly the stamp also has a compass and straight edge
on it, but it looks more like a compass and set-square (the symbols of freemasonry).  Is
there a conspiracy story behind this stamp? 

What is special about the number 17? Come along and find out how some number theory
helps to construct the heptadecagon and why pizza is not usually cut into 17 slices.