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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 720 |
| 8 | 40320 |
| 9 | 1632960 |
| 10 | 60480000 |
| 11 | 2213719200 |
| 12 | 82771476480 |
| 13 | 3211179491520 |
| 14 | 130247609057280 |
| 15 | 5542874078742000 |
| 16 | 247828800444825600 |
| 17 | 11643316737494682240 |
| 18 | 574455837701776343040 |
| 19 | 29734324379435446505280 |
| 20 | 1612668074301849600000000 |
[1,0,0,0,0,0,0,720,40320,1632960,60480000, 2213719200,82771476480,3211179491520, 130247609057280,5542874078742000, 247828800444825600,11643316737494682240, 574455837701776343040,29734324379435446505280, 1612668074301849600000000] |