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.

A068074 a(n) = Sum_{d|n} (-1)^d*2^omega(n/d) where omega(x) is the number of distinct prime factors in the factorization of x.

Table of values

n a(n)
1 -1
2 -1
3 -3
4 1
5 -3
6 -3
7 -3
8 3
9 -5
10 -3
11 -3
12 3
13 -3
14 -3
15 -9
16 5
17 -3
18 -5
19 -3
20 3
21 -9
22 -3
23 -3
24 9
25 -5
26 -3
27 -7
28 3
29 -3
30 -9
31 -3
32 7
33 -9
34 -3
35 -9
36 5
37 -3
38 -3
39 -9
40 9
41 -3
42 -9
43 -3
44 3
45 -15
46 -3
47 -3
48 15
49 -5
50 -5
51 -9
52 3
53 -3
54 -7
55 -9
56 9
57 -9
58 -3
59 -3
60 9
61 -3
62 -3
63 -15
64 9
65 -9
66 -9
67 -3
68 3
69 -9
70 -9
71 -3
72 15
73 -3
74 -3
75 -15
76 3
77 -9
78 -9
79 -3
80 15
81 -9
82 -3
83 -3
84 9
85 -9
86 -3
87 -9
88 9
89 -3

List of values

[-1, -1, -3, 1, -3, -3, -3, 3, -5, -3, -3, 3, -3, -3, -9, 5, -3, -5, -3, 3, -9, -3, -3, 9, -5, -3, -7, 3, -3, -9, -3, 7, -9, -3, -9, 5, -3, -3, -9, 9, -3, -9, -3, 3, -15, -3, -3, 15, -5, -5, -9, 3, -3, -7, -9, 9, -9, -3, -3, 9, -3, -3, -15, 9, -9, -9, -3, 3, -9, -9, -3, 15, -3, -3, -15, 3, -9, -9, -3, 15, -9, -3, -3, 9, -9, -3, -9, 9, -3]