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A130315
as a simple table
n
a(n)
1
0
2
0
3
0
4
0
5
1
6
0
7
0
8
0
9
2
10
6
11
20
12
38
13
280
14
2900
15
28399
16
293059
17
3833587
18
60167732
[0,0,0,0,1,0,0,0,2,6,20,38,280,2900,28399,293059, 3833587,60167732]