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A013140 as a simple table

na(n)
01
12
24
34
4-16
5-88
664
72496
84096
9-106624
10-480896
116875136
1254717440
13-673392640
14-7775895552
1599550288896
161454255472640
17-21279326830592
18-360442602684416
196159283224084480
20116460747215831040

[1,2,4,4,-16,-88,64,2496,4096,-106624,-480896,
 6875136,54717440,-673392640,-7775895552,
 99550288896,1454255472640,-21279326830592,
 -360442602684416,6159283224084480,
 116460747215831040]