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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.

A076543 a(n) = Sum_{k=1..n} k*sqf(k) where sqf(k)=1 if k is squarefree and sqf(k)=-1 otherwise.

Table of values

n a(n)
1 1
2 3
3 6
4 2
5 7
6 13
7 20
8 12
9 3
10 13
11 24
12 12
13 25
14 39
15 54
16 38
17 55
18 37
19 56
20 36
21 57
22 79
23 102
24 78
25 53
26 79
27 52
28 24
29 53
30 83
31 114
32 82
33 115
34 149
35 184
36 148
37 185
38 223
39 262
40 222
41 263
42 305
43 348
44 304
45 259
46 305
47 352
48 304
49 255
50 205
51 256
52 204
53 257
54 203
55 258
56 202
57 259
58 317
59 376
60 316
61 377

List of values

[1, 3, 6, 2, 7, 13, 20, 12, 3, 13, 24, 12, 25, 39, 54, 38, 55, 37, 56, 36, 57, 79, 102, 78, 53, 79, 52, 24, 53, 83, 114, 82, 115, 149, 184, 148, 185, 223, 262, 222, 263, 305, 348, 304, 259, 305, 352, 304, 255, 205, 256, 204, 257, 203, 258, 202, 259, 317, 376, 316, 377]

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

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