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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.

A381123 Number of unlabeled endofunctions on n points whose self-referencing elements are mapped from another element.

Table of values

n a(n)
0 1
1 0
2 2
3 4
4 12
5 28
6 83
7 213
8 608
9 1664
10 4703
11 13173
12 37412
13 105995
14 302301
15 862794
16 2470631
17 7084425
18 20357121
19 58573788
20 168789684
21 486964114
22 1406549550
23 4066751083
24 11769363663
25 34090076148
26 98820914068
27 286672673725
28 832183340955
29 2417270306657
30 7025657374736
31 20430883575932
32 59444386613999
33 173039084438093

List of values

[1, 0, 2, 4, 12, 28, 83, 213, 608, 1664, 4703, 13173, 37412, 105995, 302301, 862794, 2470631, 7084425, 20357121, 58573788, 168789684, 486964114, 1406549550, 4066751083, 11769363663, 34090076148, 98820914068, 286672673725, 832183340955, 2417270306657, 7025657374736, 20430883575932, 59444386613999, 173039084438093]

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

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