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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | -1 |
| 3 | -2 |
| 4 | 12 |
| 5 | 96 |
| 6 | -220 |
| 7 | -7440 |
| 8 | -15624 |
| 9 | 813120 |
| 10 | 7340112 |
| 11 | -104165280 |
| 12 | -2442773520 |
| 13 | 8815815360 |
| 14 | 855578733984 |
| 15 | 4653629425536 |
| 16 | -317564443445760 |
| 17 | -5591544140206080 |
| 18 | 110965435244017920 |
| 19 | 4730495445765296640 |
| 20 | -16883238483957574656 |
[1,0,-1,-2,12,96,-220,-7440,-15624,813120,7340112, -104165280,-2442773520,8815815360,855578733984, 4653629425536,-317564443445760,-5591544140206080, 110965435244017920,4730495445765296640, -16883238483957574656] |