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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 60 |
| 5 | 360 |
| 6 | 2520 |
| 7 | 20160 |
| 8 | 19958400 |
| 9 | 239500800 |
| 10 | 3113510400 |
| 11 | 43589145600 |
| 12 | 177843714048000 |
| 13 | 3201186852864000 |
| 14 | 60822550204416000 |
| 15 | 1216451004088320000 |
| 16 | 12926008369442488320000 |
| 17 | 310224200866619719680000 |
| 18 | 4420880996869850977271808000000 |
[1,3,12,60,360,2520,20160,19958400,239500800, 3113510400,43589145600,177843714048000, 3201186852864000,60822550204416000, 1216451004088320000,12926008369442488320000, 310224200866619719680000, 4420880996869850977271808000000] |