He is a Norwegian mathematician who provided a long-awaited elementary proof in 1948 of the prime number theorem, around the same time that [[Paul Erdős]] provided an independent proof. He immigrated to the United States and works at the Institute for Advanced Study in Princeton. | He is a Norwegian mathematician who provided a long-awaited elementary proof in 1948 of the prime number theorem, around the same time that [[Paul Erdős]] provided an independent proof. He immigrated to the United States and works at the Institute for Advanced Study in Princeton. |