Little progress had been made in solving Ramsey problems since the 1930s. Now, researchers have found the answer to r(4,t), a longstanding Ramsey problem that has perplexed the math world for decades.

Although very few people in Butte, Montana, had heard of Bertolt Brecht, it was the kind of place that Brecht would have dug: a boomtown staked out on arid highland better suited for grazing sheep, a ...