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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.

A129309 a(n) = number of primes which are < c(n) and are coprime to c(n), where c(n) is the n-th composite.

Table of values

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

List of values

[1, 1, 3, 3, 2, 3, 4, 4, 5, 5, 6, 6, 6, 7, 8, 7, 8, 7, 7, 10, 9, 9, 9, 9, 10, 10, 10, 10, 12, 12, 12, 13, 14, 13, 13, 13, 14, 14, 14, 14, 14, 14, 16, 16, 17, 16, 15, 17, 17, 16, 18, 19, 19, 19, 19, 18, 20, 21, 20, 20, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 25, 24]

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

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