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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.

A383835 Number of permutations of [n] whose compositional square is the identity permutation or its reverse.

Table of values

n a(n)
0 1
1 1
2 2
3 4
4 12
5 28
6 76
7 232
8 776
9 2632
10 9496
11 35696
12 140272
13 568624
14 2390480
15 10349536
16 46208416
17 211800992
18 997313824
19 4809701440
20 23758694336
21 119952723136
22 618884638912
23 3257843882624
24 17492191242880
25 95680444425856
26 532985208200576
27 3020676745975552

List of values

[1, 1, 2, 4, 12, 28, 76, 232, 776, 2632, 9496, 35696, 140272, 568624, 2390480, 10349536, 46208416, 211800992, 997313824, 4809701440, 23758694336, 119952723136, 618884638912, 3257843882624, 17492191242880, 95680444425856, 532985208200576, 3020676745975552]

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

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