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A104561 as a simple table

na(n)
01
1-1
21
3-2
46
5-30
6204
7-1944
823340
9-360060
106692280
11-151908120
124032593040
13-126425330640
144537069829880
15-187762669281600
168751745668796200
17-462088269954518760
1827132285729049971120
19-1779812144439507990000
20128512316060872730854560

[1,-1,1,-2,6,-30,204,-1944,23340,-360060,6692280,
 -151908120,4032593040,-126425330640,4537069829880,
 -187762669281600,8751745668796200,
 -462088269954518760,27132285729049971120,
 -1779812144439507990000,128512316060872730854560]