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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.

A211657 Sigma(k) of numbers k such that value of sigma(k) is unique; sigma(k) = A000203(k) = sum of divisors of k.

Table of values

n a(n)
1 1
2 3
3 4
4 7
5 6
6 8
7 15
8 13
9 28
10 14
11 39
12 20
13 36
14 40
15 30
16 63
17 91
18 38
19 44
20 78
21 57
22 93
23 62
24 127
25 68
26 195
27 74
28 121
29 112
30 171
31 217
32 102
33 162
34 110
35 133
36 255
37 176
38 160
39 204
40 138
41 222
42 266
43 150
44 300
45 158
46 363
47 164
48 183
49 260
50 174
51 508
52 194
53 198
54 200
55 465
56 306
57 212
58 256
59 330

List of values

[1, 3, 4, 7, 6, 8, 15, 13, 28, 14, 39, 20, 36, 40, 30, 63, 91, 38, 44, 78, 57, 93, 62, 127, 68, 195, 74, 121, 112, 171, 217, 102, 162, 110, 133, 255, 176, 160, 204, 138, 222, 266, 150, 300, 158, 363, 164, 183, 260, 174, 508, 194, 198, 200, 465, 306, 212, 256, 330]

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

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