%I #14 Nov 27 2014 15:58:19

%S 157,353,379,467,547,587,631,673,691,809,929,1291,1297,1307,1663,1669,

%T 1733,1789,1933,1997,2003,2087,2273,2309,2371,2383,2423,2441,2591,

%U 2671,2789,2909,2957,3391,3407,3511,3517,3533,3539,3559,3593,3617,3637,3851

%N Irregular primes with irregularity index two.

%C Subsequence of A060974.

%H T. D. Noe, <a href="/A073277/b073277.txt">Table of n, a(n) for n=1..10000</a> (from Buhler et al.)

%H J. Buhler, R. Crandall, R. Ernvall, T. Metsankyla and M. A. Shokrollahi, <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 <a href="/index/Be#Bernoulli">Bernoulli numbers, irregularity index of primes</a>

%t Do[p = Prime[n]; k = 1; c = 0; While[ 2*k < p - 3, If[ Mod[ Numerator[ BernoulliB[2*k]], p] == 0, c++ ]; k++ ]; If[ c == 2, Print[p]], {n, 3, 550} ]

%Y Cf. A000928, A091887, A000367, A060974, A060975 and A073276.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Jul 22 2002