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A170920 as a simple table

na(n)
1-1
2-1
3-1
4-16
5-91
6-58844
7-73267
8-1196588
9-49830764
10-1715330699
11-35249288479
12-374085503198546
13-732125336837021
14-779432268293710651
15-30015706187367326893
16-183998031852529374082
17-46789354983174555461
18-115977125342651266593554
19-248130101882943187003954597
20-13171311382437535379302071714878

[-1,-1,-1,-16,-91,-58844,-73267,-1196588,
 -49830764,-1715330699,-35249288479,
 -374085503198546,-732125336837021,
 -779432268293710651,-30015706187367326893,
 -183998031852529374082,-46789354983174555461,
 -115977125342651266593554,
 -248130101882943187003954597,
 -13171311382437535379302071714878]