Ulam spirals are maddening. I've played with them for years now, and the patterns are so close to predictable, but always break upon close inspection. I have a

Ulam spirals are maddening. I've played with them for years now, and the patterns are so close to predictable, but always break upon close inspection. I have a feeling that prime theory, and Ulam spirals in particular, will drive many mathematicians slightly crazy if they dwell on them too long. On the other hand, they create wonderful patterns. I'm getting a laser-cut Ulam spiral done to hang on my wall :-)