examples of regular primes

Examples:

1. These are all the irregular primes up to $1061$:

   37, 59, 67, 101, 103, 131, 149, 157, 233, 257, 263, 271,
   283, 293, 307, 311, 347, 353, 379, 389, 401,
   409, 421, 433, 461, 463, 467, 491, 523, 541,
   547, 557, 577, 587, 593, 607, 613, 617, 619,
   631, 647, 653, 659, 673, 677, 683, 691, 727,
   751, 757, 761, 773, 797, 809, 811, 821, 827,
   839, 877, 881, 887, 929, 953, 971, 1061.

   (for this, see the http://www.research.att.com/ njas/sequences/Seis.htmlOn-Line Encyclopedia of Integer Sequences, http://www.research.att.com/cgi-bin/access.cgi/as/njas/sequences/eisA.cgi?Anum=A000928sequence A000928)

2. The following are the first few class numbers of the cyclotomic fields $\mathbb{Q}({\zeta }_p)$, where ${\zeta }_p$ is a primitive $p$-th root of unity:

   An excellent reference for this is [1].

   Remarks:

   • Notice that $37$ divides $37$, and $59$ divides $41241=3\cdot 59\cdot 233$, thus $37,\mathrm{\hspace{0.25em}59}$ are irregular primes (see above).

   • The class number of the cyclotomic fields grows very quickly with $p$. For example, $p=19$ is the last cyclotomic field of class number 1.