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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.

A018224 a(n) = binomial(n, floor(n/2))^2 = A001405(n)^2.

Table of values

n a(n)
0 1
1 1
2 4
3 9
4 36
5 100
6 400
7 1225
8 4900
9 15876
10 63504
11 213444
12 853776
13 2944656
14 11778624
15 41409225
16 165636900
17 590976100
18 2363904400
19 8533694884
20 34134779536
21 124408576656
22 497634306624
23 1828114918084
24 7312459672336
25 27043120090000
26 108172480360000
27 402335398890000

List of values

[1, 1, 4, 9, 36, 100, 400, 1225, 4900, 15876, 63504, 213444, 853776, 2944656, 11778624, 41409225, 165636900, 590976100, 2363904400, 8533694884, 34134779536, 124408576656, 497634306624, 1828114918084, 7312459672336, 27043120090000, 108172480360000, 402335398890000]

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

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