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A100390
Numbers n where A006530 has a local minimum.
5
4, 6, 8, 12, 16, 18, 20, 24, 27, 30, 32, 36, 40, 42, 45, 48, 50, 52, 54, 56, 60, 64, 66, 68, 70, 72, 75, 77, 81, 84, 88, 90, 96, 98, 100, 102, 105, 108, 110, 112, 114, 117, 120, 125, 128, 130, 132, 135, 138, 140, 144, 147, 150, 154, 156, 160, 162, 165, 168, 175, 180
OFFSET
1,1
COMMENTS
Powers of 2 and mostly largest powers of larger primes belong here.
FORMULA
a(n) = A082418(n) + 1. - T. D. Noe, Nov 26 2007
EXAMPLE
Let gpf(n) = A006530(n). 18 is in the sequence because gpf(17) = 17 > gpf(18) = 3 < gpf(19) = 19.
MATHEMATICA
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 *)
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 *)
CROSSREFS
Cf. A006530.
Sequence in context: A310662 A231569 A337812 * A199768 A157932 A097619
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 14 2004
STATUS
approved