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.

A347890 Odd numbers k such that sigma(k) > 2*k and A003415(sigma(k)) < k, where A003415 is the arithmetic derivative, and sigma is the sum of divisors function.

Table of values

n a(n)
1 245025
2 540225
3 893025
4 2205225
5 3080025
6 4862025
7 6125625
8 6890625
9 7868025
10 10989225
11 13505625
12 14402025
13 19847025
14 22896225
15 23474025
16 26471025
17 27720225
18 29648025
19 43758225
20 45765225
21 55130625
22 57836025
23 60140025
24 65367225
25 70812225
26 72335025
27 76475025
28 77000625
29 94770225
30 121550625
31 153140625
32 156125025

List of values

[245025, 540225, 893025, 2205225, 3080025, 4862025, 6125625, 6890625, 7868025, 10989225, 13505625, 14402025, 19847025, 22896225, 23474025, 26471025, 27720225, 29648025, 43758225, 45765225, 55130625, 57836025, 60140025, 65367225, 70812225, 72335025, 76475025, 77000625, 94770225, 121550625, 153140625, 156125025]

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

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