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A023815
as a simple table
n
a(n)
0
1
1
1
2
6
3
63
4
1140
5
30730
6
1185072
7
66363206
8
7150843144
9
3829117403448
[1,1,6,63,1140,30730,1185072,66363206,7150843144, 3829117403448]