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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 24 |
| 6 | 120 |
| 7 | 360 |
| 8 | 1680 |
| 9 | 10080 |
| 10 | 72576 |
| 11 | 604800 |
| 12 | 3326400 |
| 13 | 26611200 |
| 14 | 259459200 |
| 15 | 2905943040 |
| 16 | 36324288000 |
| 17 | 290594304000 |
| 18 | 3293402112000 |
| 19 | 44460928512000 |
| 20 | 675806113382400 |
| 21 | 11263435223040000 |
| 22 | 118266069841920000 |
| 23 | 1734569024348160000 |
| 24 | 29921315670005760000 |
[1,1,1,2,6,24,120,360,1680,10080,72576,604800, 3326400,26611200,259459200,2905943040,36324288000, 290594304000,3293402112000,44460928512000, 675806113382400,11263435223040000, 118266069841920000,1734569024348160000, 29921315670005760000] |