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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.

A317581 a(1) = 1; a(n > 1) = 1 + Sum_{d|n, d mu(n/d) a(d).

Table of values

n a(n)
1 1
2 0
3 0
4 1
5 0
6 2
7 0
8 0
9 1
10 2
11 0
12 -2
13 0
14 2
15 2
16 1
17 0
18 -2
19 0
20 -2
21 2
22 2
23 0
24 4
25 1
26 2
27 0
28 -2
29 0
30 -6
31 0
32 0
33 2
34 2
35 2
36 7
37 0
38 2
39 2
40 4
41 0
42 -6
43 0
44 -2
45 -2
46 2
47 0
48 -4
49 1
50 -2
51 2
52 -2
53 0
54 4
55 2
56 4
57 2
58 2
59 0
60 16
61 0
62 2
63 -2
64 1
65 2
66 -6
67 0
68 -2
69 2
70 -6
71 0
72 -12
73 0
74 2
75 -2
76 -2
77 2
78 -6
79 0
80 -4

List of values

[1, 0, 0, 1, 0, 2, 0, 0, 1, 2, 0, -2, 0, 2, 2, 1, 0, -2, 0, -2, 2, 2, 0, 4, 1, 2, 0, -2, 0, -6, 0, 0, 2, 2, 2, 7, 0, 2, 2, 4, 0, -6, 0, -2, -2, 2, 0, -4, 1, -2, 2, -2, 0, 4, 2, 4, 2, 2, 0, 16, 0, 2, -2, 1, 2, -6, 0, -2, 2, -6, 0, -12, 0, 2, -2, -2, 2, -6, 0, -4]

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