cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A309016 Superior 2-highly composite numbers: 3-smooth numbers (A003586) k for which there is a real number e > 0 such that d(k)/k^e >= d(j)/j^e for all 3-smooth numbers j, where d(k) is the number of divisors of k (A000005).

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%I A309016 #15 May 05 2023 13:06:55
%S A309016 1,2,6,12,24,72,144,288,864,1728,5184,10368,20736,62208,124416,373248,
%T A309016 746496,1492992,4478976,8957952,26873856,53747712,107495424,322486272,
%U A309016 644972544,1289945088,3869835264,7739670528,23219011584,46438023168,92876046336,278628139008,557256278016
%N A309016 Superior 2-highly composite numbers: 3-smooth numbers (A003586) k for which there is a real number e > 0 such that d(k)/k^e >= d(j)/j^e for all 3-smooth numbers j, where d(k) is the number of divisors of k (A000005).
%C A309016 How is this related to A163895? - _R. J. Mathar_, May 05 2023
%H A309016 Michael De Vlieger, <a href="/A309016/b309016.txt">Table of n, a(n) for n = 1..2709</a>
%H A309016 Gérard Bessi, <a href="https://eudml.org/doc/181966">Etude des nombres 2-hautement composés</a>, Séminaire de Théorie des nombres de Bordeaux, Vol. 4 (1975), pp. 1-22.
%H A309016 Michael De Vlieger, <a href="/A309016/a309016.txt">Factors p analogous to A000705 such that the product of the smallest n terms equals a(n + 1)</a> (10^5 terms).
%e A309016 From _Michael De Vlieger_, Jul 12 2019: (Start)
%e A309016 We can plot all terms in A003586 with the power range 2^x with x >= 0 and 3^y with y >= 0 on the x and y axis, respectively. Plot of terms m in A309015, with terms also in a(n) placed in brackets:
%e A309016                                 2^x
%e A309016           0    1     2     3     4     5     6     7     8
%e A309016         +-----------------------------------------------------
%e A309016      0  |[1]  [2]    4
%e A309016      1  |     [6]  [12]  [24]   48
%e A309016 3^y  2  |           36   [72] [144]  [288]   576
%e A309016      3  |                216   432   [864] [1728] 3456  6912 ...
%e A309016           ...
%e A309016 Larger scale plot with "." representing a term m in A309015, and "o" representing a term in A309015 also in a(n) for all m < A002110(20).
%e A309016                               2^x
%e A309016         0    5   10   15   20   25   30   35   40   45  ...
%e A309016         +------------------------------------------------
%e A309016        0|oo.
%e A309016         | ooo.
%e A309016         |  .ooo.
%e A309016         |   ..oo..
%e A309016         |    ..ooo..
%e A309016        5|      ..oo...
%e A309016         |       ..ooo...
%e A309016         |         ..oo....
%e A309016         |          ..ooo....
%e A309016         |            ..ooo....
%e A309016       10|             ...oo.....
%e A309016         |               ..ooo....
%e A309016         |                ...oo.....
%e A309016         |                  ..ooo.....
%e A309016 3^y     |                   ...ooo....
%e A309016       15|                     ...oo.....
%e A309016         |                      ...ooo.....
%e A309016         |                        ...oo.....
%e A309016         |                         ...ooo.....
%e A309016         |                           ...oo......
%e A309016       20|                            ...ooo.....
%e A309016         |                              ...ooo.....
%e A309016         |                               ....oo......
%e A309016         |                                 ...ooo.....
%e A309016         |                                  ....oo......
%e A309016       25|                                    ...ooo......
%e A309016         |                                     ....ooo....
%e A309016         |                                       ....oo.
%e A309016         |                                        ....o
%e A309016         |                                          .
%e A309016      ...
%e A309016 (End)
%t A309016 f[nn_, k_: 2] := Block[{w = {{2, 1}, {3, 0}}, s = {2}, P = 1, q = k - 2, x, i, n, f}, f[w_List] := Log[#1, (#2 + 2)/(#2 + 1)] & @@ w; x = Array[f[w[[#]] ] &, P + 1]; For[n = 2, n <= nn, n++, i = First@ FirstPosition[x, Max[x]]; AppendTo[s, w[[i, 1]]]; w[[i, 2]]++; If[And[i > P, P <= q], P++; AppendTo[w, {Prime[i + 1], 0}]; AppendTo[x, f[Last@ w]]]; x[[i]] = f@ w[[i]] ]; s]; {1}~Join~FoldList[Times, f[32, 2]] (* _Michael De Vlieger_, Jul 11 2019, after _T. D. Noe_ at A000705 *)
%Y A309016 Subsequence of A003586 and A309015.
%Y A309016 Cf. A000005, A002201.
%K A309016 nonn
%O A309016 1,2
%A A309016 _Amiram Eldar_, Jul 06 2019
%E A309016 More terms from _Michael De Vlieger_, Jul 11 2019