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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.

A387405 a(n) is the least k that is a multiple of d=A240991(n), with abundancy ratio sigma(k)/k equal to (sigma(d)+1)/d), or -1 if no such k exists.

Table of values

n a(n)
1 18
2 54
3 196
4 1521
5 486
6 1372
7 15376
8 24025
9 4374
10 1032256
11 67228
12 39366
13 476656
14 257049
15 744775
16 27237961
17 354294
18 3341637
19 3294172
20 23088025
21 870899121
22 131096512
23 3188646
24 4990433449
25 18837288001
26 28697814
27 43647148561
28 458066416
29 161414428
30 131785698529
31 8362054027
32 274810802176
33 564736653
34 508339054441
35 258280326

List of values

[18, 54, 196, 1521, 486, 1372, 15376, 24025, 4374, 1032256, 67228, 39366, 476656, 257049, 744775, 27237961, 354294, 3341637, 3294172, 23088025, 870899121, 131096512, 3188646, 4990433449, 18837288001, 28697814, 43647148561, 458066416, 161414428, 131785698529, 8362054027, 274810802176, 564736653, 508339054441, 258280326]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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