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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.

A005817 a(n) = C(floor(n/2 + 1/2))*C(floor(n/2 + 1)) where C(i) = Catalan numbers A000108.

Table of values

n a(n)
0 1
1 1
2 2
3 4
4 10
5 25
6 70
7 196
8 588
9 1764
10 5544
11 17424
12 56628
13 184041
14 613470
15 2044900
16 6952660
17 23639044
18 81662152
19 282105616
20 987369656
21 3455793796
22 12228193432
23 43268992144
24 154532114800
25 551900410000
26 1986841476000
27 7152629313600

List of values

[1, 1, 2, 4, 10, 25, 70, 196, 588, 1764, 5544, 17424, 56628, 184041, 613470, 2044900, 6952660, 23639044, 81662152, 282105616, 987369656, 3455793796, 12228193432, 43268992144, 154532114800, 551900410000, 1986841476000, 7152629313600]

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

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