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A093496 Least k such that for every 1 < r < n there exists a distinct s, n < s <= k so that r and s have the same prime signature. 3
5, 7, 11, 13, 17, 19, 27, 49, 49, 49, 49, 49, 49, 49, 81, 81, 81, 81, 81, 81, 81, 81, 121, 169, 169, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 343, 361, 361, 361, 361, 361, 361, 361, 361, 361, 361 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

LINKS

Michael De Vlieger, Table of n, a(n) for n = 3..500

EXAMPLE

a(9) = 27. For r = 2,3,4,5,6,7,8 the corresponding s values are 11,13,25,17,10,19 and 27.

From Michael De Vlieger, Nov 26 2017: (Start)

First position n of unique values:

    a(n)     n

  ------------

      5      3

      7      4

     11      5

     13      6

     17      7

     19      8

     27      9

     49     10

     81     17

    121     25

    169     26

    343     28

    361     50

    729     65

   2401     82

   3125    243

  16807    244

(End)

MATHEMATICA

With[{s = Values@ PositionIndex@ Array[Sort[FactorInteger[#][[All, -1]], Greater] &, 10^4]}, Table[Max@ Fold[Function[{t, k}, Append[t, SelectFirst[DeleteCases[s[[FirstPosition[s, k][[1]] ]], _?(# <= n &) ], FreeQ[t, #] &]]], {}, Range[2, n - 1]], {n, 3, 60}] ] (* Michael De Vlieger, Nov 26 2017 *)

CROSSREFS

Sequence in context: A098420 A309726 A093495 * A171688 A239711 A217090

Adjacent sequences:  A093493 A093494 A093495 * A093497 A093498 A093499

KEYWORD

less,nonn

AUTHOR

Amarnath Murthy, Apr 16 2004

EXTENSIONS

More terms from David Wasserman, Oct 16 2006

STATUS

approved

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Last modified August 10 02:24 EDT 2020. Contains 336365 sequences. (Running on oeis4.)