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%I #13 Nov 27 2017 02:48:53
%S 5,7,11,13,17,19,27,49,49,49,49,49,49,49,81,81,81,81,81,81,81,81,121,
%T 169,169,343,343,343,343,343,343,343,343,343,343,343,343,343,343,343,
%U 343,343,343,343,343,343,343,361,361,361,361,361,361,361,361,361,361
%N 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.
%H Michael De Vlieger, <a href="/A093496/b093496.txt">Table of n, a(n) for n = 3..500</a>
%e 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.
%e From _Michael De Vlieger_, Nov 26 2017: (Start)
%e First position n of unique values:
%e a(n) n
%e ------------
%e 5 3
%e 7 4
%e 11 5
%e 13 6
%e 17 7
%e 19 8
%e 27 9
%e 49 10
%e 81 17
%e 121 25
%e 169 26
%e 343 28
%e 361 50
%e 729 65
%e 2401 82
%e 3125 243
%e 16807 244
%e (End)
%t 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 *)
%K less,nonn
%O 3,1
%A _Amarnath Murthy_, Apr 16 2004
%E More terms from _David Wasserman_, Oct 16 2006
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