Infinitude of regular primes

A prime $p$ is regular if it does not divide any of the Bernoulli--Seki numbers $B_2,B_4,\ldots,B_{p-3}$. Infinitude conjecture for regular primes. There exist infinitely many regular primes. This is a classical open conjecture about the distribution of primes; the paper notes that infinitude of irregular primes, in contrast, is known.