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A001548
as a simple table
n
a(n)
0
1
1
1
2
0
3
1
4
1
5
2
6
4
7
13
8
42
9
308
10
4845
11
227613
12
28639650
[1,1,0,1,1,2,4,13,42,308,4845,227613,28639650]