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:

    “I couldn’t afford to learn it,” said the Mock Turtle with a sigh. “I only took the regular course.”
    “What was that?” inquired Alice.
    “Reeling and Writhing, of course, to begin with,” the Mock Turtle replied; “and then the different branches of Arithmetic—Ambition, Distraction, Uglification, and Derision.”
    “I never heard of ‘Uglification,’” Alice ventured to say.
    Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)

    The prime purpose of being four is to enjoy being four—of secondary importance is to prepare for being five.
    Jim Trelease (20th century)