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A218917
as a simple table
n
a(n)
0
1
1
1
2
4
3
18
4
146
5
681
6
7518
7
58633
8
952826
9
11168496
10
232255571
11
3476965896
12
10867348937
13
1951392769558
[1,1,4,18,146,681,7518,58633,952826,11168496, 232255571,3476965896,10867348937,1951392769558]