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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.

A114590 Number of peaks at even levels in all hill-free Dyck paths of semilength n+2 (a hill in a Dyck path is a peak at level 1).

Table of values

n a(n)
0 1
1 2
2 8
3 28
4 103
5 382
6 1432
7 5408
8 20546
9 78436
10 300636
11 1156188
12 4459267
13 17241526
14 66807856
15 259361920
16 1008598126
17 3928120924
18 15319329472
19 59817190552
20 233826979750
21 914962032172
22 3583556424208
23 14047386554368
24 55108441878868

List of values

[1, 2, 8, 28, 103, 382, 1432, 5408, 20546, 78436, 300636, 1156188, 4459267, 17241526, 66807856, 259361920, 1008598126, 3928120924, 15319329472, 59817190552, 233826979750, 914962032172, 3583556424208, 14047386554368, 55108441878868]

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

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