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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.

A334830 a(n) is the number of permutations of length n that have the same number of fixed points whether forwards or backwards.

Table of values

n a(n)
0 1
1 1
2 0
3 0
4 14
5 46
6 200
7 1496
8 11718
9 111558
10 1052272
11 12261712
12 140348300
13 1915312460
14 25732919088
15 402510985872
16 6210501292870
17 109537725353798
18 1908681625474400
19 37475105645783072
20 727818914470269924
21 15743598127274107044
22 337206399213040703920

List of values

[1, 1, 0, 0, 14, 46, 200, 1496, 11718, 111558, 1052272, 12261712, 140348300, 1915312460, 25732919088, 402510985872, 6210501292870, 109537725353798, 1908681625474400, 37475105645783072, 727818914470269924, 15743598127274107044, 337206399213040703920]

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

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