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.

A229238 Numbers k such that phi(sigma(k))/sigma(phi(k)) = 2.

Table of values

n a(n)
1 2
2 4
3 16
4 18
5 64
6 100
7 450
8 1458
9 4096
10 4624
11 28900
12 36450
13 62500
14 65536
15 130050
16 262144
17 281250
18 1062882
19 1336336
20 3334800
21 7064400
22 8352100
23 10156800
24 10534050
25 18062500
26 21193200
27 22781250
28 26572050
29 37584450
30 39062500
31 48944016
32 81281250
33 124411716

List of values

[2, 4, 16, 18, 64, 100, 450, 1458, 4096, 4624, 28900, 36450, 62500, 65536, 130050, 262144, 281250, 1062882, 1336336, 3334800, 7064400, 8352100, 10156800, 10534050, 18062500, 21193200, 22781250, 26572050, 37584450, 39062500, 48944016, 81281250, 124411716]

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

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