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A002980 as a simple table

na(n)
01
11
20
3-1
424
5121
6-480
7-4201
848384
9478801
10-4968960
11-62871601
12885586944
1312996863881
14-203910819840
15-3476839930201
1663397697224704
171221998040867361
18-24917358603141120
19-537278342731116001

[1,1,0,-1,24,121,-480,-4201,48384,478801,-4968960,
 -62871601,885586944,12996863881,-203910819840,
 -3476839930201,63397697224704,1221998040867361,
 -24917358603141120,-537278342731116001]