A056212 Primes p whose period of reciprocal equals (p-1)/7.

211, 617, 1499, 2087, 2857, 6007, 6469, 7127, 7211, 7589, 9661, 10193, 13259, 13553, 14771, 18047, 18257, 19937, 20903, 21379, 23549, 26153, 27259, 27539, 32299, 33181, 33461, 34847, 35491, 35897, 41651, 42407, 42491, 43051, 43793

Offset: 1

Author

Robert G. Wilson v, Aug 02 2000

Keywords

• nonn
• base

Comments

Cyclic numbers of the seventh degree (or seventh order): the reciprocals of these numbers belong to one of seven different cycles. Each cycle has the (number minus 1)/7 digits.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000
• Index entries for sequences related to decimal expansion of 1/n

Crossrefs

Cf. A097443, A055628, A056157, A056210, A056211, A056213, A056214, A056215, A056216, A056217, A098680, A135073.

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, 4700]], f[ # ] == 7 &]

Extensions

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