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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 54 |
| 4 | 792 |
| 5 | 18360 |
| 6 | 628560 |
| 7 | 29801520 |
| 8 | 1864114560 |
| 9 | 148458925440 |
| 10 | 14652778694400 |
| 11 | 1754531487878400 |
| 12 | 250496910657100800 |
| 13 | 42032247882174950400 |
| 14 | 8188505926902446745600 |
| 15 | 1832839841627736125184000 |
| 16 | 467088574163438830546944000 |
[0,1,6,54,792,18360,628560,29801520,1864114560, 148458925440,14652778694400,1754531487878400, 250496910657100800,42032247882174950400, 8188505926902446745600,1832839841627736125184000, 467088574163438830546944000] |