A073277 Irregular primes with irregularity index two.

157, 353, 379, 467, 547, 587, 631, 673, 691, 809, 929, 1291, 1297, 1307, 1663, 1669, 1733, 1789, 1933, 1997, 2003, 2087, 2273, 2309, 2371, 2383, 2423, 2441, 2591, 2671, 2789, 2909, 2957, 3391, 3407, 3511, 3517, 3533, 3539, 3559, 3593, 3617, 3637, 3851

Offset: 1

Author

Robert G. Wilson v, Jul 22 2002

Keywords

• nonn

Comments

Subsequence of A060974.

Links

• T. D. Noe, Table of n, a(n) for n=1..10000 (from Buhler et al.)
• J. Buhler, R. Crandall, R. Ernvall, T. Metsankyla and M. A. Shokrollahi, Irregular Primes and Cyclotomic Invariants to 12 Million, J. Symbolic Computation 31, 2001, 89-96.
• Bernoulli numbers, irregularity index of primes

Crossrefs

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

Programs

Mathematica

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} ]