The related concepts of Lagrange and Markov spectra have intrigued me since my student years; nowadays I study them using geometric methods in homogeneous dynamics, a strategy with roots in the 50s and 60s starting with W.Schmidt and brought to prominence by Dani, Margulis, Kazhdan and others. I had the good fortune to be invited for lectures at Tata by Dani and Yale by Margulis, and I hope one day to reciprocate the…
I've never been able to perceive the beauty that others such as yourself can see. Genuine question, where do you see the beauty? All I see in your link is a wall of equations, although I have a maths background it's all abstract and I can't get anything out of it.
There is a lot going on for summing 3 squares. It is fun and unexpected. All the weirder because they don't seem to have linked all this to pi, e or i yet in an obvious way looking at the wiki page.