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A121187
as a simple table
n
a(n)
4
1
5
4
6
22
7
126
8
686
9
3640
10
19470
11
103889
12
558389
13
3019000
14
16443467
[1,4,22,126,686,3640,19470,103889,558389,3019000, 16443467]