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A254433
as a simple table
n
a(n)
1
1
2
1
3
3
4
12
5
140
6
3950
7
263707
8
42285095
9
16825391023
10
17095967464466
11
45375565948693336
[1,1,3,12,140,3950,263707,42285095,16825391023, 17095967464466,45375565948693336]