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A006925
as a simple table
n
a(n)
0
0
1
0
2
0
3
0
4
0
5
1
6
2
7
8
8
48
9
450
10
5751
11
90553
12
1612905
13
31297357
14
652159389
15
14499780660
16
342646718608
[0,0,0,0,0,1,2,8,48,450,5751,90553,1612905, 31297357,652159389,14499780660,342646718608]