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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5038 |
| 8 | 40004 |
| 9 | 347348 |
| 10 | 3165888 |
| 11 | 29362568 |
| 12 | 272387290 |
| 13 | 2509750674 |
| 14 | 22933267716 |
| 15 | 207994616888 |
| 16 | 1875239211676 |
| 17 | 16832320088082 |
| 18 | 150613964836684 |
| 19 | 1344743911906806 |
| 20 | 11988640129482008 |
| 21 | 106774648037691852 |
| 22 | 950340529566921394 |
| 23 | 8454752823292244122 |
[1,1,2,6,24,120,720,5038,40004,347348,3165888, 29362568,272387290,2509750674,22933267716, 207994616888,1875239211676,16832320088082, 150613964836684,1344743911906806, 11988640129482008,106774648037691852, 950340529566921394,8454752823292244122] |