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A220471
as a simple table
n
a(n)
1
1
2
2
3
9
4
40
5
238
6
1564
7
11807
8
98529
9
904318
10
9006364
11
96709332
12
1110858977
13
13581942434
14
175844515544
[1,2,9,40,238,1564,11807,98529,904318,9006364, 96709332,1110858977,13581942434,175844515544]