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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 4 |
| 3 | 12 |
| 4 | 48 |
| 5 | 240 |
| 6 | 1440 |
| 7 | 10080 |
| 8 | 80640 |
| 9 | 725760 |
| 10 | 7257600 |
| 11 | 79833600 |
| 12 | 958003200 |
| 13 | 12454041600 |
| 14 | 174356582400 |
| 15 | 2615348736000 |
| 16 | 41845579776000 |
| 17 | 711374856192000 |
| 18 | 12804747411456000 |
| 19 | 243290200817664000 |
| 20 | 4865804016353280000 |
| 21 | 102181884343418880000 |
| 22 | 2248001455555215360000 |
[0,2,4,12,48,240,1440,10080,80640,725760,7257600, 79833600,958003200,12454041600,174356582400, 2615348736000,41845579776000,711374856192000, 12804747411456000,243290200817664000, 4865804016353280000,102181884343418880000, 2248001455555215360000] |