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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.

A042971 a(n) = (C(2n, n)/2 - (2^(n-1) + ((n+1) mod 2)*C(n-1, n/2-1)))/2.

Table of values

n a(n)
1 0
2 0
3 3
4 12
5 55
6 210
7 826
8 3136
9 12027
10 45870
11 175846
12 674784
13 2598102
14 10024196
15 38771188
16 150250496
17 583368787
18 2268706134
19 8836184878
20 34461323872
21 134563944322
22 526023515996
23 2058355584748
24 8061896050432
25 31602643220830
26 123979613859660
27 486734822857596

List of values

[0, 0, 3, 12, 55, 210, 826, 3136, 12027, 45870, 175846, 674784, 2598102, 10024196, 38771188, 150250496, 583368787, 2268706134, 8836184878, 34461323872, 134563944322, 526023515996, 2058355584748, 8061896050432, 31602643220830, 123979613859660, 486734822857596]

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

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