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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.

A376579 Least prime p such that p*n+1 is prime, or -1 if no such prime exists.

Table of values

n a(n)
1 2
2 2
3 2
4 3
5 2
6 2
7 -1
8 2
9 2
10 3
11 2
12 3
13 -1
14 2
15 2
16 7
17 -1
18 2
19 -1
20 2
21 2
22 3
23 2
24 3
25 -1
26 2
27 -1
28 7
29 2
30 2
31 -1
32 3
33 2
34 3
35 2
36 2
37 -1
38 5
39 2
40 7
41 2
42 3
43 -1
44 2
45 -1
46 3
47 -1
48 2
49 -1
50 2
51 2
52 3
53 2
54 2
55 -1
56 2
57 -1
58 19
59 -1
60 3
61 -1
62 5
63 2
64 3
65 2
66 3
67 -1
68 2
69 2
70 3
71 -1
72 13
73 -1
74 2
75 2
76 3
77 -1
78 2
79 -1
80 3
81 2
82 19

List of values

[2, 2, 2, 3, 2, 2, -1, 2, 2, 3, 2, 3, -1, 2, 2, 7, -1, 2, -1, 2, 2, 3, 2, 3, -1, 2, -1, 7, 2, 2, -1, 3, 2, 3, 2, 2, -1, 5, 2, 7, 2, 3, -1, 2, -1, 3, -1, 2, -1, 2, 2, 3, 2, 2, -1, 2, -1, 19, -1, 3, -1, 5, 2, 3, 2, 3, -1, 2, 2, 3, -1, 13, -1, 2, 2, 3, -1, 2, -1, 3, 2, 19]

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