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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 48 |
| 5 | 240 |
| 6 | 1440 |
| 7 | 10080 |
| 8 | 120960 |
| 9 | 1088640 |
| 10 | 10886400 |
| 11 | 119750400 |
| 12 | 1916006400 |
| 13 | 24908083200 |
| 14 | 348713164800 |
| 15 | 5230697472000 |
| 16 | 104613949440000 |
| 17 | 1778437140480000 |
| 18 | 32011868528640000 |
| 19 | 608225502044160000 |
[1,1,2,6,48,240,1440,10080,120960,1088640, 10886400,119750400,1916006400,24908083200, 348713164800,5230697472000,104613949440000, 1778437140480000,32011868528640000, 608225502044160000] |