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.

A080403 Numbers n such that both A000203(n) and A001157(n) are squarefree: sum of divisors and squares of divisors of n are squarefree.

Table of values

n a(n)
1 1
2 2
3 4
4 5
5 8
6 9
7 13
8 16
9 18
10 20
11 25
12 29
13 37
14 49
15 50
16 61
17 64
18 72
19 73
20 80
21 101
22 109
23 113
24 116
25 117
26 121
27 122
28 128
29 137
30 144
31 148
32 169
33 173
34 181
35 200
36 208
37 218
38 229
39 242
40 244
41 261
42 277
43 281
44 289
45 292
46 313
47 317
48 320
49 325
50 333
51 353
52 362
53 373
54 389
55 397
56 401
57 404
58 409

List of values

[1, 2, 4, 5, 8, 9, 13, 16, 18, 20, 25, 29, 37, 49, 50, 61, 64, 72, 73, 80, 101, 109, 113, 116, 117, 121, 122, 128, 137, 144, 148, 169, 173, 181, 200, 208, 218, 229, 242, 244, 261, 277, 281, 289, 292, 313, 317, 320, 325, 333, 353, 362, 373, 389, 397, 401, 404, 409]

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

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