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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.

A257561 Number of permutations of length n that avoid the patterns 4231, 4312, and 4321.

Table of values

n a(n)
0 1
1 1
2 2
3 6
4 21
5 80
6 322
7 1346
8 5783
9 25372
10 113174
11 511649
12 2338988
13 10793251
14 50205607
15 235156609
16 1108120540
17 5249646137
18 24987770893
19 119443412277
20 573125649031
21 2759515312908
22 13328311926552
23 64559295743113
24 313530998739472
25 1526333617345412
26 7447070497787110
27 36409703715788374
28 178353171835771153
29 875224495042876048
30 4302111437028045585

List of values

[1, 1, 2, 6, 21, 80, 322, 1346, 5783, 25372, 113174, 511649, 2338988, 10793251, 50205607, 235156609, 1108120540, 5249646137, 24987770893, 119443412277, 573125649031, 2759515312908, 13328311926552, 64559295743113, 313530998739472, 1526333617345412, 7447070497787110, 36409703715788374, 178353171835771153, 875224495042876048, 4302111437028045585]

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

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