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A228005 as a simple table

na(n)
20
3-2
41
5-2
6-72
7-672
8136
94352
10-265600
11602048
122658941440
13128532940800
147138246144
15-277070036992
16-5928696847474688
17140393397382594560
18-476899996446720000
1973073105939334987776
20-197109670210161672192

[0,-2,1,-2,-72,-672,136,4352,-265600,602048,
 2658941440,128532940800,7138246144,-277070036992,
 -5928696847474688,140393397382594560,
 -476899996446720000,73073105939334987776,
 -197109670210161672192]