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A012779 as a simple table

na(n)
01
10
2-1
33
4-18
560
6-180
7-1050
824192
9-308952
103131760
11-23742840
1262587272
132606501040
14-75839636600
151415140435800
16-20144425867712
17187207018203392
18730860552463104
19-93674690778135744

[1,0,-1,3,-18,60,-180,-1050,24192,-308952,3131760,
 -23742840,62587272,2606501040,-75839636600,
 1415140435800,-20144425867712,187207018203392,
 730860552463104,-93674690778135744]