My impression, not checked against evidence, is that my recaps here feature the 2019 series more than any other. Well, I really liked the 2019 series. I don’t think that’s just recentism. On rereading them, I often feel little pleasant surprises along the way. That’s a good feeling.
So here was my ‘F’ entry for 2019: Fourier series. They’re important. They’re built out of easy pieces, though. And they’re full of weird bits. You can understand why someone would spend a career studying them. And I almost give enough information to actually use the things, if you have enough background to understand how to use them. I like hitting that sweet spot.