This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A046415 #25 Feb 16 2025 08:32:39
%S A046415 8,9,10,14,41,43,49,53,109,157,167,173,197,199,223,229,269,283,307,349
%N A046415 Repunit of length a(n) has exactly 4 prime factors (counted with multiplicity).
%H A046415 P. De Geest, <a href="https://www.worldofnumbers.com/repunits.htm">Repunits prime factors</a>
%H A046415 Makoto Kamada, <a href="https://stdkmd.net/nrr/repunit/">Factorizations of 11...11 (Repunit)</a>
%H A046415 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Repunit.html">Repunit</a>
%t A046415 Select[Range[350],PrimeOmega[FromDigits[PadRight[{},#,1]]]==4&] (* _Harvey P. Dale_, Oct 27 2020 *)
%o A046415 (PARI) isok(n) = bigomega((10^n - 1)/9) == 4; \\ _Michel Marcus_, Apr 23 2017
%Y A046415 Cf. A000042, A001222, A002275, A004022, A004023, A046053.
%K A046415 nonn,base,more
%O A046415 1,1
%A A046415 _Patrick De Geest_, Jul 15 1998
%E A046415 More terms from _Robert Gerbicz_, Nov 22 2010
%E A046415 Offset corrected to 1, a(18)-a(20) added by _Ray Chandler_, Apr 23 2017