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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.

A237839 a(n) = |{0 < k <= n: q = |{p <= k*n: p and p + 2 are both prime}| and q + 2 are both prime}|.

Table of values

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

List of values

[0, 0, 0, 2, 1, 3, 2, 3, 1, 2, 2, 3, 3, 2, 2, 5, 2, 3, 3, 4, 2, 2, 2, 3, 1, 2, 2, 3, 3, 2, 3, 2, 2, 3, 6, 7, 5, 5, 3, 4, 3, 3, 4, 3, 3, 4, 4, 4, 5, 4, 5, 3, 3, 4, 3, 2, 2, 3, 4, 3, 4, 3, 3, 6, 6, 5, 5, 4, 5, 3, 5, 8, 4, 3, 3, 4, 1, 3, 4, 3]

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