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A012904 as a simple table

na(n)
00
12
2-1
311
4-30
5215
6-1095
79200
8-67060
9676565
10-6364125
1175816050
12-870716550
1312014125175
14-162677426275
152556597056000
16-39838813521000
17703292880031625
18-12389158068197625
19242880759376082750

[0,2,-1,11,-30,215,-1095,9200,-67060,676565,
 -6364125,75816050,-870716550,12014125175,
 -162677426275,2556597056000,-39838813521000,
 703292880031625,-12389158068197625,
 242880759376082750]