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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.

A188664 a(n) = 2A(n)/C(n) where A(n) = A180874(n) and C(n) = Catalan(n) = A000108(n).

Table of values

n a(n)
1 2
2 1
3 2
4 8
5 52
6 495
7 6470
8 111034
9 2419928
10 65269092
11 2133844440
12 83133090480
13 3805035352536
14 202147745618247
15 12336516593999598
16 857054350280418290
17 67247553674224203280
18 5917723267088513913032
19 580407202154922558537264
20 63093021853191022229671056
21 7563270705677373923076693840

List of values

[2, 1, 2, 8, 52, 495, 6470, 111034, 2419928, 65269092, 2133844440, 83133090480, 3805035352536, 202147745618247, 12336516593999598, 857054350280418290, 67247553674224203280, 5917723267088513913032, 580407202154922558537264, 63093021853191022229671056, 7563270705677373923076693840]

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

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