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
Examples
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...
Links
- M. Kamada, Factorization of 11...11(Repunits)
Extensions
Corrected and extended by Hans Havermann, Jun 22 2006
a(25)-a(33) from Ray Chandler, May 09 2017