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A002019 as a simple table

na(n)
01
11
21
3-1
4-7
55
6145
7-5
8-6095
9-5815
10433025
11956375
12-46676375
13-172917875
147108596625
1538579649875
16-1454225641375
17-10713341611375
18384836032842625
193663118565923375
20-127950804666254375
21-1519935859717136875

[1,1,1,-1,-7,5,145,-5,-6095,-5815,433025,956375,
 -46676375,-172917875,7108596625,38579649875,
 -1454225641375,-10713341611375,384836032842625,
 3663118565923375,-127950804666254375,
 -1519935859717136875]