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

1,1

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

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} ]

Crossrefs

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

Sequence in context: A346431 A234364 A060974 * A180233 A096708 A142833

Adjacent sequences: A073274 A073275 A073276 * A073278 A073279 A073280

Keyword

nonn

Author

Robert G. Wilson v, Jul 22 2002

Status

approved