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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.

A307912 a(n) = n - 1 - pi(2*n-1) + pi(n), where pi is the prime counting function.

Table of values

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

List of values

[0, 0, 1, 1, 3, 3, 4, 5, 5, 5, 7, 7, 9, 10, 10, 10, 12, 13, 14, 15, 15, 15, 17, 17, 18, 19, 19, 20, 22, 22, 23, 24, 25, 25, 26, 26, 27, 28, 29, 29, 31, 31, 33, 34, 34, 35, 37, 38, 38, 39, 39, 39, 41, 41, 41, 42, 42, 43, 45, 46, 48, 49, 50, 50, 51, 51, 53, 54]

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

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