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A215253
as a simple table
n
a(n)
1
1
2
2
3
4
4
9
5
18
6
37
7
77
8
150
9
333
10
601
11
1202
12
2405
13
4941
14
9622
15
21325
16
38489
17
76978
18
153957
[1,2,4,9,18,37,77,150,333,601,1202,2405,4941,9622, 21325,38489,76978,153957]