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A018905
as a simple table
n
a(n)
0
2
1
4
2
9
3
21
4
50
5
120
6
289
7
697
8
1682
9
4060
10
9801
11
23661
12
57122
13
137904
14
332929
[2,4,9,21,50,120,289,697,1682,4060,9801,23661, 57122,137904,332929]