Quanta Magazine charts how erdosproblems.com — a hobbyist catalogue of the 1,200-plus problems Paul Erdős left behind — became the arena where AI labs now test their machine mathematicians. OpenAI models cracked the 80-year-old unit distance problem in May and three more Erdős problems on August 1; Google DeepMind has solved four, recovered nine forgotten solutions, and autonomously closed 9 of 353 formally posed problems. The site now counts 565 problems solved against 652 still open, and Erdős problems concentrate in number theory and combinatorics — exactly where language models are strongest.