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A011803
as a simple table
n
a(n)
-1
1
0
2
1
8
2
64
3
904
4
20926
5
753994
6
40412530
7
3099627142
8
329518779600
[1,2,8,64,904,20926,753994,40412530,3099627142, 329518779600]