A217611 Primes p such that the octal expansion of 1/p has a unique period length.

3, 7, 19, 73, 87211, 262657, 18837001, 77158673929, 5302306226370307681801, 19177458387940268116349766612211, 6113142872404227834840443898241613032969, 328017025014102923449988663752960080886511412965881

Offset: 1

Author

Arkadiusz Wesolowski, Oct 08 2012

Keywords

• base
• nonn

Comments

Also called generalized unique primes in base 8.

Links

• Arkadiusz Wesolowski, Table of n, a(n) for n = 1..27
• C. K. Caldwell, "Top Twenty" page, Generalized Unique
• Wikipedia, Octal

Crossrefs

Cf. A019326, A040017 (unique-period primes in base 10).

Programs

Mathematica

lst = {}; Do[c = Cyclotomic[n, 8]; q = c/GCD[n, c]; If[PrimePowerQ[q], p = FactorInteger[q][[1, 1]]; AppendTo[lst, p]], {n, 138}]; Sort[lst]