The numbers k from sequence S000894.
1, 2, 3, 4, 5, 6, 8, 7, 9, 10, 12, 15, 16, 13, 14, 18, 20, 24, 21, 11, 22, 30, 17, 27, 25, 28, 32, 36, 31, 40, 42, 45, 35, 48, 37, 19, 50, 33, 54, 60, 56, 26, 64, 63, 44, 72, 52, 80, 67, 70, 39, 84, 75, 49, 90, 66, 96, 81, 55, 100, 108, 112, 94, 120, 38, 62, 105
1
Note how some prime numbers take a long time to appear. Why?
T. D. Noe, Plot of 105 terms
T. D. Noe, Table of 105 terms
(Mma) nn = 10^6; t3 = Table[0, {Floor[Sqrt[nn]]}]; t4 = {}; found = 0; Do[c = Length[Select[Divisors[n], # < Sqrt[n] &]]; If[c > 0 && c <= nn && t3[[c]] == 0, t3[[c]] = n; AppendTo[t4, {n, c}]; found++], {n, nn}]; Transpose[t4][[2]]
nonn
T. D. Noe, May 19 2016