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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.

A330557 a(n) = number of primes p <= 2*n+1 with Delta(p) == 2 mod 4, where Delta(p) = nextprime(p) - p.

Table of values

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

List of values

[0, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 7, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 10, 11, 12, 12, 12, 12, 12, 13, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 15, 15, 15, 16, 16, 16, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 20, 21, 21]

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