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A109721
as a simple table
n
a(n)
0
1
1
3
2
21
3
77
4
252
5
567
6
1051
7
1465
8
1674
9
1465
10
1051
11
567
12
252
13
77
14
21
15
3
16
1
[1,3,21,77,252,567,1051,1465,1674,1465,1051,567, 252,77,21,3,1]