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A006455
as a simple table
n
a(n)
0
1
1
1
2
2
3
7
4
40
5
357
6
4824
7
96428
8
2800472
9
116473461
10
6855780268
11
565505147444
12
64824245807684
[1,1,2,7,40,357,4824,96428,2800472,116473461, 6855780268,565505147444,64824245807684]