“Then, in November 2021, Granville opened up an email from Larsen, then 17 years old and in his senior year of high school.”
Mathematicians proved in 1994 that there are infinitely many Carmichael numbers, then got stuck for decades on where they show up. A 17-year-old in Bloomington proved there’s always one between X and 2X, using the Maynard and Tao prime gap work. The surprise isn’t the kid. It’s that the experts actually opened an unsolicited email from a high schooler and read the attachment.