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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.

A162977 Number of fixed points in all reverse alternating (i.e., up-down) permutations of {1,2,...,n}.

Table of values

n a(n)
1 1
2 2
3 1
4 4
5 15
6 62
7 257
8 1384
9 7679
10 50522
11 346113
12 2702764
13 22022143
14 199360982
15 1881735169
16 19391512144
17 207983607807
18 2404879675442
19 28880901505025
20 370371188237524
21 4922617151619071
22 69348874393137902
23 1010501269355233281

List of values

[1, 2, 1, 4, 15, 62, 257, 1384, 7679, 50522, 346113, 2702764, 22022143, 199360982, 1881735169, 19391512144, 207983607807, 2404879675442, 28880901505025, 370371188237524, 4922617151619071, 69348874393137902, 1010501269355233281]

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

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