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.

A321268 Number of permutations on [n] whose up-down signature has nonnegative partial sums and which have exactly two descents.

Table of values

n a(n)
1 0
2 0
3 0
4 0
5 22
6 172
7 856
8 3488
9 12746
10 43628
11 143244
12 457536
13 1434318
14 4438540
15 13611136
16 41473216
17 125797010
18 380341580
19 1147318004
20 3455325600
21 10394291094
22 31242645420
23 93853769320
24 281825553760
25 846030314842
26 2539248578732
27 7620161662556
28 22865518160768

List of values

[0, 0, 0, 0, 22, 172, 856, 3488, 12746, 43628, 143244, 457536, 1434318, 4438540, 13611136, 41473216, 125797010, 380341580, 1147318004, 3455325600, 10394291094, 31242645420, 93853769320, 281825553760, 846030314842, 2539248578732, 7620161662556, 22865518160768]

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

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