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A011789
as a simple table
n
a(n)
0
1
1
4
2
22
3
126
4
748
5
4532
6
27853
7
172965
8
1082628
9
6818768
10
43163792
11
274370868
12
1750133503
[1,4,22,126,748,4532,27853,172965,1082628,6818768, 43163792,274370868,1750133503]