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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.

A321269 Number of permutations on [n] whose up-down signature has nonnegative partial sums and which have exactly three descents.

Table of values

n a(n)
1 0
2 0
3 0
4 0
5 0
6 0
7 604
8 7296
9 54746
10 330068
11 1756878
12 8641800
13 40298572
14 180969752
15 790697160
16 3385019968
17 14270283414
18 59457742524
19 245507935018
20 1006678811272
21 4105447763032
22 16672235476128
23 67482738851220
24 272439143364672
25 1097660274098482
26 4415486996246052

List of values

[0, 0, 0, 0, 0, 0, 604, 7296, 54746, 330068, 1756878, 8641800, 40298572, 180969752, 790697160, 3385019968, 14270283414, 59457742524, 245507935018, 1006678811272, 4105447763032, 16672235476128, 67482738851220, 272439143364672, 1097660274098482, 4415486996246052]

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

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