Paper was posted on arXiv by Zhi-Wei Sun, a mathematician at Nanjing University. He says he used GPT-5.6 Sol. I can't judge it's significance personally, but the models all say this is a very big deal if it holds up, and a historic breakthrough in number theory. It was sent to me by Jimmy Apples who saw it first. https://arxiv.org/abs/2609.04176