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A000644
as a simple table
n
a(n)
1
1
2
1
3
3
4
7
5
31
6
138
7
808
8
4956
9
33047
10
227328
11
1614793
12
11710299
13
86495618
14
648399937
15
4923728056
[1,1,3,7,31,138,808,4956,33047,227328,1614793, 11710299,86495618,648399937,4923728056]