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A007871
as a simple table
n
a(n)
1
1
2
1
3
3
4
12
5
66
6
420
7
3200
8
27144
9
258705
10
2704592
11
30898506
12
381922380
13
5090938955
[1,1,3,12,66,420,3200,27144,258705,2704592, 30898506,381922380,5090938955]