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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.

A354830 a(n) is the number of permutations p of [n] such that gcd(i, p(i)) > 1 for 2 <= i <= n.

Table of values

n a(n)
0 1
1 1
2 1
3 1
4 2
5 2
6 8
7 8
8 30
9 72
10 408
11 408
12 4104
13 4104
14 29640
15 208704
16 1437312
17 1437312
18 22653504
19 22653504
20 318695040
21 2686493376
22 27628410816
23 27628410816
24 575372874240
25 1775480841216
26 21115550048256
27 132879856582656
28 2321256928702464
29 2321256928702464
30 83095013944442880

List of values

[1, 1, 1, 1, 2, 2, 8, 8, 30, 72, 408, 408, 4104, 4104, 29640, 208704, 1437312, 1437312, 22653504, 22653504, 318695040, 2686493376, 27628410816, 27628410816, 575372874240, 1775480841216, 21115550048256, 132879856582656, 2321256928702464, 2321256928702464, 83095013944442880]

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

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