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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.

A248511 Difference between k and the least prime factor of k^2+1 where k is the n-th number with k^2+1 composite.

Table of values

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

List of values

[1, 3, 5, 3, 7, 9, 7, 11, 13, 15, 13, 17, 19, 17, 21, 23, 25, 23, 27, 13, 29, 27, 31, 21, 33, 35, 33, 37, 39, 37, 41, 31, 43, 17, 45, 43, 47, 9, 49, 47, 51, 53, 55, 53, 57, 47, 59, 57, 61, 47, 63, 65, 63, 67, 57, 69, 67, 71, 73, 23, 75, 73, 77, 43, 79, 77, 81]

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

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