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

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