A072859 - OEIS

A072859

Primes p for which the period of 1/p is prime.

11, 37, 41, 53, 79, 83, 107, 173, 227, 239, 271, 317, 347, 359, 467, 479, 563, 587, 643, 719, 733, 773, 797, 839, 907, 1031, 1187, 1231, 1283, 1307, 1319, 1439, 1493, 1523, 1627, 1637, 1879, 1907, 1987, 2027, 2039, 2467, 2477, 2677, 2791, 2837, 2879, 2963

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OFFSET

1,1

COMMENTS

Primes p such that the multiplicative order of 10 (mod p) is prime. - Joerg Arndt, Oct 26 2014

Together with 3, complement in primes of A249330. - Arkadiusz Wesolowski, Oct 25 2014

LINKS

Ray Chandler, Table of n, a(n) for n = 1..10000

EXAMPLE

1/37 = 0. 027 027 ... with period = 3, hence 37 is in the sequence.

MATHEMATICA

Select[Prime[Range[500]], PrimeQ[MultiplicativeOrder[10, #]]&] (* Ray Chandler, Oct 31 2011 *)