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A089498
as a simple table
n
a(n)
0
0
1
4
2
20
3
120
4
696
5
4060
6
23660
7
137904
8
803760
9
4684660
10
27304196
11
159140520
[0,4,20,120,696,4060,23660,137904,803760,4684660, 27304196,159140520]