Whether or not that's true, and I doubt that it is, we all know who is hands down the wittiest. I'm stuck on 1.3.21. What the hell is "the 1,2,1 pattern or the

Whether or not that's true, and I doubt that it is, we all know who is hands down the wittiest. I'm stuck on 1.3.21. What the hell is "the 1,2,1 pattern or the -1,2,-1 pattern"? Does he mean a pattern in the columns? I see 1,2,1 but not -1,2,-1. Is this like one of those duck-rabbit optical illusions? Edit: there is, however, a -1,2,-1 pattern in 1.3.24, and the system there is very similar to the one in 1.3.21.