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%I #17 Dec 12 2021 20:11:33
%S 4,6,8,12,16,18,20,24,27,30,32,36,40,42,45,48,50,52,54,56,60,64,66,68,
%T 70,72,75,77,81,84,88,90,96,98,100,102,105,108,110,112,114,117,120,
%U 125,128,130,132,135,138,140,144,147,150,154,156,160,162,165,168,175,180
%N Numbers n where A006530 has a local minimum.
%C Powers of 2 and mostly largest powers of larger primes belong here.
%H T. D. Noe, <a href="/A100390/b100390.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = A082418(n) + 1. - _T. D. Noe_, Nov 26 2007
%e Let gpf(n) = A006530(n). 18 is in the sequence because gpf(17) = 17 > gpf(18) = 3 < gpf(19) = 19.
%t mxp[x_] := Max[FactorInteger[x][[All, 1]]]; ta = {{0}}; Do[s1 = mxp[n - 1]; s = mxp[n]; s2 = mxp[n + 1]; If[Greater[s1, s] && Greater[s2, s], Print[{n, {s1, s, s2}}]; ta = Append[ta, n]], {n, 1, 512}]; ta = Delete[ta, 1] (* Original program edited by _Michael De Vlieger_, Mar 26 2017 *)
%t With[{n = 181}, Select[MapIndexed[{First@ #2 + 1, Differences@ #1} &, Partition[Array[FactorInteger[#][[-1, 1]] &, n], 3, 1]], Apply[And[#1 < 0, #2 > 0] &, Last@ #] &][[All, 1]]] (* _Michael De Vlieger_, Mar 26 2017 *)
%Y Cf. A006530.
%K nonn
%O 1,1
%A _Labos Elemer_, Dec 14 2004