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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.

A259922 a(n)= Sum_{2 < prime p <= n} c_p - Sum_{n < prime p < 2*n} c_p, where 2^c_p is the greatest power of 2 dividing p-1.

Table of values

n a(n)
1 0
2 -1
3 -1
4 -2
5 2
6 1
7 1
8 1
9 -3
10 -4
11 -2
12 -3
13 1
14 1
15 -1
16 -2
17 6
18 6
19 6
20 6
21 3
22 2
23 4
24 3
25 3
26 3
27 1
28 1
29 5
30 4
31 4
32 4
33 4
34 3
35 3
36 2
37 3
38 3
39 3
40 2
41 8
42 7
43 9
44 9
45 6
46 6
47 8
48 8
49 3
50 3
51 1
52 0
53 4
54 3
55 1
56 1
57 -3
58 -3
59 -1
60 -1
61 3
62 3
63 3
64 2
65 2
66 1
67 3
68 3
69 0
70 -1
71 1
72 1
73 7
74 7
75 5
76 4
77 4
78 4
79 4
80 4
81 4
82 3

List of values

[0, -1, -1, -2, 2, 1, 1, 1, -3, -4, -2, -3, 1, 1, -1, -2, 6, 6, 6, 6, 3, 2, 4, 3, 3, 3, 1, 1, 5, 4, 4, 4, 4, 3, 3, 2, 3, 3, 3, 2, 8, 7, 9, 9, 6, 6, 8, 8, 3, 3, 1, 0, 4, 3, 1, 1, -3, -3, -1, -1, 3, 3, 3, 2, 2, 1, 3, 3, 0, -1, 1, 1, 7, 7, 5, 4, 4, 4, 4, 4, 4, 3]