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 A100393 #16 May 10 2022 12:48:38
%S A100393 26,34,49,51,55,65,69,76,86,94,99,111,116,118,122,129,134,142,146,155,
%T A100393 161,183,185,188,202,206,209,214,218,237,244,246,249,254,265,267,274,
%U A100393 287,291,295,298,302,305,309,321,326,329,334,339,341,344,351,356,362
%N A100393 Composite numbers k such that Gpf(k-1) < Gpf(k) > Gpf(k+1), where Gpf = A006530.
%C A100393 A006530(k) is the largest prime factor of k.
%H A100393 Robert Israel, <a href="/A100393/b100393.txt">Table of n, a(n) for n = 1..10000</a>
%e A100393 26 is in the sequence because the largest prime factors of 25, 26, and 27 are 5, 13, and 3, respectively.
%p A100393 gpf:= n -> max(numtheory:-factorset(n)):
%p A100393 L:= map(gpf, [$1..1000]):
%p A100393 select(t -> L[t]<> t and L[t]>L[t-1] and L[t]>L[t+1], [$2..nops(L)-1]); # _Robert Israel_, Jul 12 2018
%t A100393 <<NumberTheory`NumberTheoryFunctions` mxp[x_] :=Max[PrimeFactorList[x]]; lf[x_] :=Length[PrimeFactorList[x]]; ta={{0}};Do[s1=mxp[n-1];s=mxp[n];s2=mxp[n+1]; If[Greater[s, s1]&&Greater[s, s2]&&!PrimeQ[n], Print[{n, {s1, s, s2}}];ta=Append[ta, n]], {n, 1, 1000}];ta=Delete[ta, 1]
%t A100393 Select[Flatten[Position[Partition[Table[FactorInteger[n][[-1,1]],{n,400}],3,1],_?(#[[1]]< #[[2]]> #[[3]]&),1,Heads->False]],CompositeQ[#+1]&]+1 (* _Harvey P. Dale_, May 10 2022 *)
%Y A100393 Cf. A006530, A100390, A100392.
%K A100393 nonn
%O A100393 1,1
%A A100393 _Labos Elemer_, Dec 14 2004
%E A100393 Edited by _Don Reble_, Jun 13 2007