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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.

A018784 Numbers n such that sigma(phi(n)) = n.

Table of values

n a(n)
1 1
2 3
3 15
4 28
5 255
6 744
7 2418
8 20440
9 65535
10 548856
11 2835756
12 4059264
13 4451832
14 10890040
15 13192608
16 23001132
17 54949482
18 110771178
19 220174080
20 445701354
21 4294967295
22 16331433888
23 18377794080
24 94951936080
25 204721968000
26 386940247200
27 601662398400
28 1433565580920

List of values

[1, 3, 15, 28, 255, 744, 2418, 20440, 65535, 548856, 2835756, 4059264, 4451832, 10890040, 13192608, 23001132, 54949482, 110771178, 220174080, 445701354, 4294967295, 16331433888, 18377794080, 94951936080, 204721968000, 386940247200, 601662398400, 1433565580920]

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

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