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A009407 as a simple table

na(n)
00
11
2-1
3-1
40
5-11
615
727
8-504
97785
10-74025
11835735
12-9654216
13121643677
14-1646734089
1523833558707
16-368032192080
176033531089873
18-104751319907313
191920112851095471
20-37066806679606640
21751794216181100869

[0,1,-1,-1,0,-11,15,27,-504,7785,-74025,835735,
 -9654216,121643677,-1646734089,23833558707,
 -368032192080,6033531089873,-104751319907313,
 1920112851095471,-37066806679606640,
 751794216181100869]