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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.

A345655 a(n) is the number of permutations w of [n] with no w(i)+1 == w(i+1) (mod n) that are not simply cyclic permutations of the numbers 1 to n in backwards order.

Table of values

n a(n)
1 0
2 0
3 0
4 0
5 35
6 210
7 1596
8 12992
9 118863
10 1202870
11 13361392
12 161638752
13 2115684259
14 29792671818
15 449145795900
16 7217975402752
17 123180993414207
18 2224874726830638
19 42402252681323840
20 850380681002034880
21 17902407539998807875
22 394741856473979171586
23 9097740802923890621468

List of values

[0, 0, 0, 0, 35, 210, 1596, 12992, 118863, 1202870, 13361392, 161638752, 2115684259, 29792671818, 449145795900, 7217975402752, 123180993414207, 2224874726830638, 42402252681323840, 850380681002034880, 17902407539998807875, 394741856473979171586, 9097740802923890621468]

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

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