A119761 Values n such that the largest prime factor of repunit R_n=(10^n -1)/9 is a unique prime,i.e.,whose reciprocal has unique decimal period length.

2, 3, 4, 6, 9, 10, 12, 14, 18, 19, 23, 24, 36, 38, 39, 46, 48, 62, 78, 93, 96, 106, 120, 134, 150, 186, 196, 240, 268, 294, 300, 317, 320

Offset

1,1

Links

Table of n, a(n) for n=1..33.

M. Kamada, Factorization of 11...11(Repunits)

Example

18 is in the sequence because R_18=3^2*7*11*13*19*37*52579*333667 and 333667 is the only prime with period 9: 1/333667 =0.000002997000002997...

Crossrefs

Cf. A002275, A003020, A007498, A040017.

Sequence in context: A026439 A285082 A249602 * A144429 A260194 A014851

Adjacent sequences: A119758 A119759 A119760 * A119762 A119763 A119764

Keyword

more,nonn,base

Author

Lekraj Beedassy, Jun 18 2006

Extensions

Corrected and extended by Hans Havermann, Jun 22 2006

a(25)-a(33) from Ray Chandler, May 09 2017

Status

approved