A056211 Primes p whose period of reciprocal equals (p-1)/6.

79, 547, 643, 751, 907, 997, 1201, 1213, 1237, 1249, 1483, 1489, 1627, 1723, 1747, 1831, 1879, 1987, 2053, 2551, 2683, 3049, 3253, 3319, 3613, 3919, 4159, 4507, 4519, 4801, 4813, 4831, 4969, 5119, 5443, 5557, 5791, 6079, 6151, 6271, 6373, 6427, 6529

Offset: 1

Author

Robert G. Wilson v, Aug 02 2000

Keywords

• nonn
• base

Comments

Cyclic numbers of the sixth degree (or sixth order): the reciprocals of these numbers belong to one of six different cycles. Each cycle has the (number minus 1)/6 digits.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)
• Index entries for sequences related to decimal expansion of 1/n

Crossrefs

Cf. A001913, A097443, A055628, A056157, A056210, A056212, A056213, A056214, A056215, A056216, A056217, A098680.

Programs

Mathematica

f[n_Integer] := Block[{ds = Divisors[n - 1]}, (n - 1)/Take[ ds, Position[ PowerMod[ 10, ds, n], 1] [[1, 1]]] [[ -1]]]; Select[ Prime[ Range[4, 850]], f[ # ] == 6 &]

Extensions

Edited by N. J. A. Sloane, Apr 30 2007