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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.

A255369 a(n) = (sigma(n)-n-1)*(2-mu(n)), where sigma(n) is the sum of the divisors of n and mu(n) is the Möbius function.

Table of values

n a(n)
1 -1
2 0
3 0
4 4
5 0
6 5
7 0
8 12
9 6
10 7
11 0
12 30
13 0
14 9
15 8
16 28
17 0
18 40
19 0
20 42
21 10
22 13
23 0
24 70
25 10
26 15
27 24
28 54
29 0
30 123
31 0
32 60
33 14
34 19
35 12
36 108
37 0
38 21
39 16
40 98
41 0
42 159
43 0
44 78
45 64
46 25
47 0
48 150
49 14
50 84
51 20
52 90
53 0
54 130
55 16
56 126
57 22
58 31
59 0
60 214
61 0
62 33
63 80
64 124
65 18
66 231
67 0
68 114

List of values

[-1, 0, 0, 4, 0, 5, 0, 12, 6, 7, 0, 30, 0, 9, 8, 28, 0, 40, 0, 42, 10, 13, 0, 70, 10, 15, 24, 54, 0, 123, 0, 60, 14, 19, 12, 108, 0, 21, 16, 98, 0, 159, 0, 78, 64, 25, 0, 150, 14, 84, 20, 90, 0, 130, 16, 126, 22, 31, 0, 214, 0, 33, 80, 124, 18, 231, 0, 114]

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