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A057394 as a simple table

na(n)
01
10
20
3-4
4-12
5-60
6-220
7-936
8-4092
9-17840
10-80868
11-356172
12-1640872
13-7433604
14-34541160
15-159080304
16-743832276
17-3469487112
18-16321682424
19-76796957940
20-363235185312
21-1720415299660
22-8176521038556

[1,0,0,-4,-12,-60,-220,-936,-4092,-17840,-80868,
 -356172,-1640872,-7433604,-34541160,-159080304,
 -743832276,-3469487112,-16321682424,-76796957940,
 -363235185312,-1720415299660,-8176521038556]