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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 3 |
| 4 | 6 |
| 5 | 30 |
| 6 | 180 |
| 7 | 1260 |
| 8 | 10080 |
| 9 | 90720 |
| 10 | 907200 |
| 11 | 9979200 |
| 12 | 119750400 |
| 13 | 1556755200 |
| 14 | 21794572800 |
| 15 | 326918592000 |
| 16 | 5230697472000 |
| 17 | 88921857024000 |
| 18 | 1600593426432000 |
| 19 | 30411275102208000 |
| 20 | 608225502044160000 |
| 21 | 12772735542927360000 |
| 22 | 281000181944401920000 |
[1,3,6,30,180,1260,10080,90720,907200,9979200, 119750400,1556755200,21794572800,326918592000, 5230697472000,88921857024000,1600593426432000, 30411275102208000,608225502044160000, 12772735542927360000,281000181944401920000] |