Crazy constructible polygons

Read on Prof Ian Stewart’s Twitter (@JoatStewart):

“Regular 618046320536701272583608037733434096317263320037227965361869850786715388113584129-gon is constructible with ruler compass & trisector

So is 756760676272923020551154471073240459834492063891235892290277703256956240171581788957704193-gon. 90-digit prime!

However, regular 11-gon is not constructible with ruler, compass, and angle-trisector. Next impossible cases 22, 23, 25, 29.

It gets crazier. Gleason conjectured there are infinitely many primes of form 2^c.3^d+1. About 9k with k digits or less”

 

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