cp's OEIS Frontend

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.

A257546 Number of permutations of length n such that numbers at odd positions are monotone and numbers at even positions are also monotone.

Table of values

n a(n)
0 1
1 1
2 2
3 6
4 24
5 40
6 80
7 140
8 280
9 504
10 1008
11 1848
12 3696
13 6864
14 13728
15 25740
16 51480
17 97240
18 194480
19 369512
20 739024
21 1410864
22 2821728
23 5408312
24 10816624
25 20801200
26 41602400
27 80233200
28 160466400
29 310235040
30 620470080
31 1202160780
32 2404321560
33 4667212440

List of values

[1, 1, 2, 6, 24, 40, 80, 140, 280, 504, 1008, 1848, 3696, 6864, 13728, 25740, 51480, 97240, 194480, 369512, 739024, 1410864, 2821728, 5408312, 10816624, 20801200, 41602400, 80233200, 160466400, 310235040, 620470080, 1202160780, 2404321560, 4667212440]

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

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