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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | -4 |
| 5 | -8 |
| 6 | 0 |
| 7 | -56 |
| 8 | 1136 |
| 9 | -4976 |
| 10 | 47040 |
| 11 | -541728 |
| 12 | 2460416 |
| 13 | -51170624 |
| 14 | 202185984 |
| 15 | -5359238912 |
| 16 | 20705351936 |
| 17 | -673408564736 |
| 18 | 2215089472512 |
| 19 | -100278515381760 |
| 20 | 202372883465216 |
| 21 | -17008883052323840 |
[0,1,0,0,-4,-8,0,-56,1136,-4976,47040,-541728, 2460416,-51170624,202185984,-5359238912, 20705351936,-673408564736,2215089472512, -100278515381760,202372883465216, -17008883052323840] |