Regular Prime

In number theory, a regular prime is a prime number p > 2 that does not divide the class number of the p-th cyclotomic field.

The first few regular primes are:

3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 41, ... (sequence A007703 in OEIS)
List of unsolved problems in mathematics
Are there infinitely many regular primes, and if so is their relative density ?

Read more about Regular Prime:  Kummer's Criterion, Properties, Irregular Primes, Irregular Pairs, History

Famous quotes containing the words regular and/or prime:

    “The solid and well-defined fir-tops, like sharp and regular spearheads, black against the sky, gave a peculiar, dark, and sombre look to the forest.”
    —Henry David Thoreau (1817–1862)

    “Being prime minister is a lonely job.... you cannot lead from the crowd.”
    —Margaret Thatcher (b. 1925)