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A006407
as a simple table
n
a(n)
3
1
4
1
5
2
6
4
7
8
8
20
9
58
10
177
11
630
12
2410
13
9772
14
41423
15
181586
16
814412
17
3722445
[1,1,2,4,8,20,58,177,630,2410,9772,41423,181586, 814412,3722445]