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A140980
as a simple table
n
a(n)
0
1
1
1
2
2
3
5
4
15
5
52
6
202
7
856
8
3868
9
18313
10
89711
11
450825
12
2310453
[1,1,2,5,15,52,202,856,3868,18313,89711,450825, 2310453]