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 A079747 #14 Jun 05 2022 08:30:15 %S A079747 2,9,10,21,22,25,28,33,46,57,58,78,82,85,91,92,93,106,115,121,126,133, %T A079747 136,141,145,148,166,169,170,171,172,176,177,178,190,201,205,213,217, %U A079747 221,222,226,232,235,236,248,253,261,262,276,289,290,301,316,325,346 %N A079747 Numbers k such that gpf(k-1) < gpf(k) < gpf(k+1), where gpf(k) is the greatest prime factor of k (A006530). %C A079747 Numbers k such that A079748(k-1) > 1. %H A079747 T. D. Noe, <a href="/A079747/b079747.txt">Table of n, a(n) for n=1..1000</a> %F A079747 a(n) = A071869(n-1) + 1. - _T. D. Noe_, Nov 26 2007 %e A079747 k=25: 25-1 = 24 = 3*2^3, 25 = 5^2 and 25+1 = 26 = 13*2, therefore 25 is a term (3 < 5 < 13). %t A079747 gpf[n_] := FactorInteger[n][[-1, 1]]; ind = Position[Differences[Array[gpf, 350]], _?(# > 0 &)] // Flatten; ind[[Position[Differences[ind], 1] // Flatten]] + 1 (* _Amiram Eldar_, Jun 05 2022 *) %Y A079747 Cf. A071869, A071870, A082417-A082422. %K A079747 nonn %O A079747 1,1 %A A079747 _Reinhard Zumkeller_, Jan 10 2003