A051627 Periods associated with A040017.

1, 2, 3, 4, 10, 12, 9, 14, 24, 36, 48, 38, 19, 23, 39, 62, 120, 150, 106, 93, 134, 294, 196, 320, 654, 738, 385, 586, 317, 597, 1404, 945, 1452, 1836, 1752, 1172, 1812, 1282, 1426, 2232, 1862, 1844, 1521, 2134, 3750, 1031, 2264, 2667, 4354, 3927, 4274, 6522, 3903, 6022, 6682, 6135, 9550, 5877

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• nice
• base

Comments

The numbers in A007498 sorted according to the magnitude of the corresponding prime. - T. D. Noe, Sep 08 2005

Examples

			The decimal expansion of 1/101 is 0.00990099..., having a period of 4 and it is the only prime with that period.
		

Links

• Ray Chandler, Table of n, a(n) for n = 1..99
• C. K. Caldwell, Unique Primes
• Eric Weisstein's World of Mathematics, Unique Prime
• Index entries for sequences related to decimal expansion of 1/n

Programs

Mathematica

nmax = 10000; primesPeriods = Reap[Do[p = Cyclotomic[n, 10]/GCD[n, Cyclotomic[n, 10]]; If[PrimeQ[p], Print[n]; Sow[{p, n}]], {n, 1, nmax}]][[2, 1]]; Sort[primesPeriods][[All, 2]] // Prepend[#, 1]& // Take[#, 58]& (* Jean-François Alcover, Mar 29 2013 *)

Formula

a(n) = A002371(A000720(A040017(n))). - Max Alekseyev, Oct 14 2022

Extensions

More terms from Jud McCranie

More terms from T. D. Noe, Sep 08 2005

Corrected a(45)=3750 and extended by Ray Chandler, Oct 13 2008