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A060975 Irregular primes with irregularity index three. 11
491, 617, 647, 1151, 1217, 1811, 1847, 2939, 3833, 4003, 4657, 4951, 6763, 7687, 8831, 9011, 10463, 10589, 12073, 13217, 14533, 14737, 14957, 15287, 15787, 15823, 16007, 17681, 17863, 18713, 18869, 20533, 20939, 24019, 24659, 25153, 26561 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

T. D. Noe, Table of n, a(n) for n=1..9824 (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 == 3, Print[p]], {n, 3, 1000} ]

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 == 3, Print@p], {n, 3, 13887} ]

CROSSREFS

Cf. A000928, A000367, A060974, A060975, A073276 and A073277.

Sequence in context: A056052 A051115 A273809 * A180457 A271664 A082079

Adjacent sequences:  A060972 A060973 A060974 * A060976 A060977 A060978

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Jul 22 2002

EXTENSIONS

Extended by Robert G. Wilson v, Sep 20 2006

STATUS

approved

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Last modified August 18 19:41 EDT 2017. Contains 290762 sequences.