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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.

A121530 Number of double rises at an odd level in all nondecreasing Dyck paths of semilength n. A nondecreasing Dyck path is a Dyck path for which the sequence of the altitudes of the valleys is nondecreasing.

Table of values

n a(n)
1 0
2 1
3 4
4 14
5 47
6 148
7 454
8 1359
9 4004
10 11644
11 33521
12 95696
13 271300
14 764605
15 2143964
16 5985186
17 16643779
18 46124692
19 127433562
20 351106955
21 964976460
22 2646158176
23 7241414949
24 19779499584
25 53933402472
26 146828245753
27 399137621524

List of values

[0, 1, 4, 14, 47, 148, 454, 1359, 4004, 11644, 33521, 95696, 271300, 764605, 2143964, 5985186, 16643779, 46124692, 127433562, 351106955, 964976460, 2646158176, 7241414949, 19779499584, 53933402472, 146828245753, 399137621524]

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

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