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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 4320 |
| 8 | 22920 |
| 9 | 112056 |
| 10 | 525642 |
| 11 | 2441314 |
| 12 | 11467387 |
| 13 | 55213453 |
| 14 | 269051424 |
| 15 | 1315752712 |
| 16 | 6425315520 |
| 17 | 31265476224 |
| 18 | 151611449472 |
| 19 | 733893891840 |
| 20 | 3552247523904 |
| 21 | 17205089767968 |
| 22 | 83394449973808 |
| 23 | 404426778909176 |
[1,2,6,24,120,720,4320,22920,112056,525642, 2441314,11467387,55213453,269051424,1315752712, 6425315520,31265476224,151611449472,733893891840, 3552247523904,17205089767968,83394449973808, 404426778909176] |