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A155456 as a simple table

na(n)
0-1
1-1
21
3-2
46
5-24
6120
7-720
85040
9-40320
10362880
11-3628800
1239916800
13-479001600
146227020800
15-87178291200
161307674368000
17-20922789888000
18355687428096000
19-6402373705728000
20121645100408832000

[-1,-1,1,-2,6,-24,120,-720,5040,-40320,362880,
 -3628800,39916800,-479001600,6227020800,
 -87178291200,1307674368000,-20922789888000,
 355687428096000,-6402373705728000,
 121645100408832000]