Seeking a math-related article about strange infinite series

Post date: 2019-09-13 14:14:32

My Google-foo is failing me. About a month ago, I started reading a very interesting article about a topic in mathematics. I read only the first few paragraphs before I got distracted by something. Now I want to finish the article, but I can't find it.

I'm not a mathematician, so I might be getting some details wrong, but this is how I remember it. The article talked about infinite series that seem like they're going to converge to a specific value (like pi or e), but then unexpectedly start to diverge away from that value after X number of terms. And as I recall, X can be fairly small, like 20 terms. Or, in some cases, it can be huge, like 10^10 terms.

I can't remember if the article had some overall point beyond just describing these strange series, but I know it wasn't an academic paper. It was published in some kind of popular outlet, like Quanta, Nautilus, or Seed.

It's not in my browser history, and I've had no success in Googling it. It's possible that I'm not remembering the specifics correctly, so I might be using the wrong search terms.

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