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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.

A254569 The number of unordered pairs (f,g) of functions from {1..n} to itself such that fg=gf (i.e., f(g(i))=g(f(i)) for all i).

Table of values

n a(n)
1 1
2 7
3 84
4 1540
5 37345
6 1145376
7 42402871
8 1849021504
9 93217426857
10 5363120671120
11 348669188664511
12 25418305492373520
13 2064813985107357445
14 185896884170249831320
15 18459391640792004885375
16 2012607682674617326564096
17 239898601216105901349115537
18 31132586664410794285693925664
19 4380971763246528510240944123071
20 665896706682993760478978112600400

List of values

[1, 7, 84, 1540, 37345, 1145376, 42402871, 1849021504, 93217426857, 5363120671120, 348669188664511, 25418305492373520, 2064813985107357445, 185896884170249831320, 18459391640792004885375, 2012607682674617326564096, 239898601216105901349115537, 31132586664410794285693925664, 4380971763246528510240944123071, 665896706682993760478978112600400]

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

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