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A006220
as a simple table
n
a(n)
1
1
2
1
3
3
4
10
5
45
6
251
7
1638
8
12300
9
104877
10
1000135
11
10534062
12
121436206
13
1521332904
[1,1,3,10,45,251,1638,12300,104877,1000135, 10534062,121436206,1521332904]