A046418 Repunit of length a(n) has exactly 7 prime factors (counted with multiplicity).
12, 20, 21, 22, 27, 35, 61, 65, 74, 82, 85, 141, 146, 177, 187, 194, 226, 299, 323, 329, 337
Offset: 1
Links
- P. De Geest, Repunits prime factors
- Makoto Kamada, Factorizations of 11...11 (Repunit)
- Eric Weisstein's World of Mathematics, Repunit
Programs
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Mathematica
Select[Range[300],PrimeOmega[FromDigits[PadRight[{},#,1]]]==7&] (* Harvey P. Dale, Feb 04 2019 *)
Extensions
More terms from Robert Gerbicz, Nov 22 2010
Changed offset to 1, a(18) added by Ray Chandler, Apr 23 2017
a(19)-a(21) from Max Alekseyev, May 14 2022