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 A303659 #12 Feb 16 2025 08:33:54
%S A303659 2,5,6,24,27,28,79,1171,1901,1932,7845,19152,360698,649358,1731441,
%T A303659 1979944,30658517,34337898,400114748,412626117,3738454462,7725156081,
%U A303659 97366414806,129951504625,290788509485
%N A303659 Numbers k such that the average of greatest prime factors of all positive integers <= k is an integer.
%C A303659 Numbers k such that (k - 1) | (A046670(k) - 1).
%C A303659 Numbers k such that (k - 1) | A088822(k).
%C A303659 a(26) > 10^12. - _Giovanni Resta_, May 05 2018
%H A303659 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GreatestPrimeFactor.html">Greatest Prime Factor</a>
%e A303659 6 is in the sequence because (gpf(2) + gpf(3) + gpf(4) + gpf(5) + gpf(6))/5 = (2 + 3 + 2 + 5 + 3)/5 = 3 is an integer.
%o A303659 (PARI) isok(n) = (n>1) && !(sum(k=2, n, vecmax(factor(k)[,1])) % (n-1)); \\ _Michel Marcus_, Apr 29 2018
%o A303659 (PARI) lista(nn) = {s = 0; for (n=2, nn, s += vecmax(factor(n)[,1]); if (! (s % (n-1)), print1(n, ", ")););} \\ _Michel Marcus_, Apr 29 2018
%Y A303659 Cf. A006530, A046670, A088822, A226647, A284755, A303480, A303482.
%K A303659 nonn,more
%O A303659 1,1
%A A303659 _Ilya Gutkovskiy_, Apr 28 2018
%E A303659 a(13)-a(18) from _Michel Marcus_, Apr 29 2018
%E A303659 a(19)-a(25) from _Giovanni Resta_, May 05 2018