cp's OEIS Frontend

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.

A131119 a(n) = (-1)^n * Sum_{i=1..floor(n/2)} i * floor(n/(n-i)).

Table of values

n a(n)
0 0
1 0
2 2
3 -1
4 5
5 -3
6 9
7 -6
8 14
9 -10
10 20
11 -15
12 27
13 -21
14 35
15 -28
16 44
17 -36
18 54
19 -45
20 65
21 -55
22 77
23 -66
24 90
25 -78
26 104
27 -91
28 119
29 -105
30 135
31 -120
32 152
33 -136
34 170
35 -153
36 189
37 -171
38 209
39 -190
40 230
41 -210
42 252
43 -231
44 275
45 -253
46 299
47 -276
48 324
49 -300
50 350
51 -325
52 377
53 -351
54 405

List of values

[0, 0, 2, -1, 5, -3, 9, -6, 14, -10, 20, -15, 27, -21, 35, -28, 44, -36, 54, -45, 65, -55, 77, -66, 90, -78, 104, -91, 119, -105, 135, -120, 152, -136, 170, -153, 189, -171, 209, -190, 230, -210, 252, -231, 275, -253, 299, -276, 324, -300, 350, -325, 377, -351, 405]