%I #32 Aug 24 2018 01:59:17
%S 2,3,37,157,491,12613,78233,527377,3238481,381348997,1767218027
%N Smallest prime of irregularity index n.
%C By convention 2 has irregularity index -1; regular primes (the first is 3, see A007703) have index 0; an irregular prime of index n >= 1 is an irregular prime p (see A000928) such that p divides exactly n Bernoulli numbers B_{2i} with 2i < p-1.
%D P. Ribenboim, The New Book of Prime Number Records, Springer-Verlag, NY, 1995, page 326.
%D Paulo Ribenboim, The Little Book of Bigger Primes, Second Edition, Springer-Verlag, NY, 2004, page 226.
%H J. Buhler, R. Crandall, R. Ernvall and T. Metsankyla, <a href="http://dx.doi.org/10.1090/S0025-5718-1993-1197511-5">Irregular primes and cyclotomic invariants to four million</a>, Math. Comp. 61 (1993), no. 203, 151-153.
%H J. P. Buhler, R. E. Crandall, R. Ernvall et al., <a href="http://dx.doi.org/10.1006/jsco.1999.1011">Irregular primes and cyclotomic invariants to 12 Million</a>, J. Symbolic Computation 31 (2001) 89-96.
%H W. Hart, D. Harvey and W. Ong, <a href="https://doi.org/10.1090/mcom/3211">Irregular primes to two billion</a>, Mathematics of Computation, 86 (2017), 3031-3049; also available at <a href="https://arxiv.org/abs/1605.02398">arXiv:1605.02398 [math.NT]</a>, 2016.
%H Math. Pages, <a href="http://www.mathpages.com/home/kmath411.htm">On the Density of Some Exceptional Primes</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/IrregularPrime.html">Irregular Prime.</a>
%H <a href="/index/Be#Bernoulli">Bernoulli numbers, irregularity index of primes</a>
%Y Cf. A091887, A000928, A007703, A073276, A073277, A060975, A219332, A219333, A219334, A219335, A297848.
%K nonn,nice,hard,more
%O -1,1
%A William G. McCallum (wmc(AT)math.arizona.edu) and _Robert G. Wilson v_, May 20 2001
%E a(8)-a(9) added by _Amiram Eldar_, Aug 23 2018 from the paper by Hart et al.