|
%I #15 Dec 12 2021 20:11:48
%S 3,5,7,11,13,17,19,23,26,29,31,34,37,41,43,47,49,51,53,55,59,61,65,67,
%T 69,71,73,76,79,83,86,89,94,97,99,101,103,107,109,111,113,116,118,122,
%U 127,129,131,134,137,139,142,146,149,151,155,157,161,163,167,173,179
%N Numbers k such that A006530(k-1) < A006530(k) > A006530(k+1).
%C A006530(k) is the largest prime factor of k.
%C The sequence contains all odd primes.
%H T. D. Noe, <a href="/A100392/b100392.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = A082417(n) + 1. - _T. D. Noe_, Nov 26 2007
%e 26 is here because the largest prime factors of 25, 26, 27 are 5, 13, 3.
%t <<NumberTheory`NumberTheoryFunctions` mxp[x_] :=Max[PrimeFactorList[x]];ta={{0}}; Do[s1=mxp[n-1];s=mxp[n];s2=mxp[n+1]; If[Greater[s, s1]&&Greater[s, s2], Print[{n, {s1, s, s2}}]; ta=Append[ta, n]], {n, 1, 1000}]ta=Delete[ta, 1]
%t With[{lpfs=Table[FactorInteger[n][[-1,1]],{n,200}]},Flatten[Position[ Partition[ lpfs,3,1],_?(First[#]<#[[2]]>Last[#]&),{1},Heads-> False]]+ 1] (* _Harvey P. Dale_, Feb 22 2014 *)
%Y Cf. A006530, A100390, A100393.
%K nonn
%O 1,1
%A _Labos Elemer_, Dec 14 2004
%E Edited by _Don Reble_, Jun 13 2007
|
