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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.

A320042 a(n) = a(floor(n/2)) + (-1)^(n*(n+1)/2) with a(1)=0.

Table of values

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

List of values

[0, -1, 1, 0, -2, 0, 2, 1, -1, -3, -1, 1, -1, 1, 3, 2, 0, -2, 0, -2, -4, -2, 0, 2, 0, -2, 0, 2, 0, 2, 4, 3, 1, -1, 1, -1, -3, -1, 1, -1, -3, -5, -3, -1, -3, -1, 1, 3, 1, -1, 1, -1, -3, -1, 1, 3, 1, -1, 1, 3, 1, 3, 5, 4, 2, 0, 2, 0, -2, 0, 2, 0, -2, -4, -2, 0, -2, 0, 2, 0]