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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 4320 |
| 8 | 25920 |
| 9 | 155520 |
| 10 | 858120 |
| 11 | 4498296 |
| 12 | 23026074 |
| 13 | 117437746 |
| 14 | 604907611 |
| 15 | 3173843821 |
| 16 | 16812885360 |
| 17 | 89389649752 |
| 18 | 475278119520 |
| 19 | 2522515936704 |
| 20 | 13358285027136 |
| 21 | 70620776750592 |
| 22 | 372942661980096 |
| 23 | 1968609876492672 |
[1,2,6,24,120,720,4320,25920,155520,858120, 4498296,23026074,117437746,604907611,3173843821, 16812885360,89389649752,475278119520, 2522515936704,13358285027136,70620776750592, 372942661980096,1968609876492672] |