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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.

A323807 Number of permutations p of [n] such that max_{j=1..n} |p(j)-j| = floor(n/2).

Table of values

n a(n)
1 1
2 1
3 2
4 9
5 23
6 157
7 503
8 4833
9 18827
10 234061
11 1076807
12 16447329
13 87358763
14 1583571277
15 9541763303
16 200258110593
17 1350025656107
18 32202026068621
19 240183024181127
20 6418149695049249
21 52479230675397803
22 1553052337531253197
23 13814973114258788903
24 448537638127408597953
25 4312466658317635366187

List of values

[1, 1, 2, 9, 23, 157, 503, 4833, 18827, 234061, 1076807, 16447329, 87358763, 1583571277, 9541763303, 200258110593, 1350025656107, 32202026068621, 240183024181127, 6418149695049249, 52479230675397803, 1553052337531253197, 13814973114258788903, 448537638127408597953, 4312466658317635366187]

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

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