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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.

A139130 a(n) = Sum_{k=1..n} d(d(k)), where d(k) = number of divisors of k.

Table of values

n a(n)
1 1
2 3
3 5
4 7
5 9
6 12
7 14
8 17
9 19
10 22
11 24
12 28
13 30
14 33
15 36
16 38
17 40
18 44
19 46
20 50
21 53
22 56
23 58
24 62
25 64
26 67
27 70
28 74
29 76
30 80
31 82
32 86
33 89
34 92
35 95
36 98
37 100
38 103
39 106
40 110
41 112
42 116
43 118
44 122
45 126
46 129
47 131
48 135
49 137
50 141
51 144
52 148
53 150
54 154
55 157
56 161
57 164
58 167
59 169
60 175
61 177
62 180

List of values

[1, 3, 5, 7, 9, 12, 14, 17, 19, 22, 24, 28, 30, 33, 36, 38, 40, 44, 46, 50, 53, 56, 58, 62, 64, 67, 70, 74, 76, 80, 82, 86, 89, 92, 95, 98, 100, 103, 106, 110, 112, 116, 118, 122, 126, 129, 131, 135, 137, 141, 144, 148, 150, 154, 157, 161, 164, 167, 169, 175, 177, 180]

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

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