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A290048 as a simple table

na(n)
21
3-552
48640
5116000
6-4868460
767855536
8-544522240
92742137280
10-8237774250
1110592091400
123366617856
13113971542048
14-1217020425880
154535746506000
16-5415752171520
17-19090509870144
1893580817811453
19-142801363479240
20-80721277168000
21665065363025280

[1,-552,8640,116000,-4868460,67855536,-544522240,
 2742137280,-8237774250,10592091400,3366617856,
 113971542048,-1217020425880,4535746506000,
 -5415752171520,-19090509870144,93580817811453,
 -142801363479240,-80721277168000,665065363025280]