%I #23 Aug 11 2024 14:41:31

%S 28,51,55,58,77,86,95,98,107,115,119,124,155,161,193,209,217,218,221,

%T 233,253,265,295,298,303,314,346

%N Repunit of length a(n) has exactly 8 prime factors (counted with multiplicity).

%H P. De Geest, <a href="https://www.worldofnumbers.com/repunits.htm">Repunits prime factors</a>

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/repunit/">Factorizations of 11...11 (Repunit)</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Repunit.html">Repunit</a>

%t Select[Range[320],PrimeOmega[FromDigits[Table[1,#]]]==8&] (* _Harvey P. Dale_, Sep 04 2018 *)

%Y Cf. A000042, A001222, A002275, A004022, A004023, A046053.

%K nonn,base,more

%O 1,1

%A _Patrick De Geest_, Jul 15 1998

%E More terms from _Robert Gerbicz_, Nov 22 2010

%E Offset changed to 1, a(23)-a(26) added by _Ray Chandler_, Apr 23 2017

%E a(27) from _Max Alekseyev_, May 14 2022