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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 5 |
| 4 | 22 |
| 5 | 114 |
| 6 | 696 |
| 7 | 4920 |
| 8 | 39600 |
| 9 | 357840 |
| 10 | 3588480 |
| 11 | 39553920 |
| 12 | 475372800 |
| 13 | 6187104000 |
| 14 | 86699289600 |
| 15 | 1301447347200 |
| 16 | 20835611596800 |
| 17 | 354379753728000 |
| 18 | 6381450915840000 |
| 19 | 121289412980736000 |
| 20 | 2426499634470912000 |
[1,5,22,114,696,4920,39600,357840,3588480, 39553920,475372800,6187104000,86699289600, 1301447347200,20835611596800,354379753728000, 6381450915840000,121289412980736000, 2426499634470912000] |