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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 240 |
| 6 | 2880 |
| 7 | 40320 |
| 8 | 645120 |
| 9 | 11612160 |
| 10 | 232243200 |
| 11 | 5109350400 |
| 12 | 122624409600 |
| 13 | 3188234649600 |
| 14 | 89270570188800 |
| 15 | 2678117105664000 |
| 16 | 85699747381248000 |
| 17 | 2913791410962432000 |
| 18 | 104896490794647552000 |
[0,0,0,0,24,240,2880,40320,645120,11612160, 232243200,5109350400,122624409600,3188234649600, 89270570188800,2678117105664000,85699747381248000, 2913791410962432000,104896490794647552000] |