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A086912
as a simple table
n
a(n)
1
1
2
4
3
8
4
20
5
80
6
476
7
3832
8
39886
9
518314
10
8177364
11
153154356
12
3343378690
13
83803337868
14
2381994458224
[1,4,8,20,80,476,3832,39886,518314,8177364, 153154356,3343378690,83803337868,2381994458224]