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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.

A161120 Number of cycles with entries of opposite parities in all fixed-point-free involutions of {1,2,...,2n}.

Table of values

n a(n)
0 0
1 1
2 4
3 27
4 240
5 2625
6 34020
7 509355
8 8648640
9 164189025
10 3445942500
11 79222218075
12 1979900722800
13 53443570205025
14 1549547301802500
15 48028060502296875
16 1584712538529120000
17 55458748565165570625

List of values

[0, 1, 4, 27, 240, 2625, 34020, 509355, 8648640, 164189025, 3445942500, 79222218075, 1979900722800, 53443570205025, 1549547301802500, 48028060502296875, 1584712538529120000, 55458748565165570625]

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

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