A.M.Gleason has proved that a regular polygon of sides can be constructed by ruler, compass and angle-trisector if and only if , where the 's are distinct Pierpont primes.
Compare with the polygons constructible with ruler and compass only.
The first Pierpont primes are 2, 3, 5, 7, 13, 17, 19, 37, 73, 97, 109, 163, 193, 257, 433, 487, 577, 769, 1153, 1297, 1459, 2593, 2917, 3457, 3889, 10369, 12289, 17497, 18433, 39367, 52489, 65537, 139969, 147457, 209953 more terms