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| n | a(n) |
|---|---|
| 0 | 6 |
| 1 | 102 |
| 2 | 1008 |
| 3 | 7860 |
| 4 | 53340 |
| 5 | 330372 |
| 6 | 1918224 |
| 7 | 10615176 |
| 8 | 56602260 |
| 9 | 293032740 |
| 10 | 1481004096 |
| 11 | 7337198232 |
| 12 | 35743534008 |
| 13 | 171641101800 |
| 14 | 814046047200 |
| 15 | 3819148459920 |
| 16 | 17747499595140 |
| 17 | 81776562767460 |
| 18 | 373968175442400 |
| 19 | 1698587342436600 |
| 20 | 7667851012141320 |
| 21 | 34422129328312440 |
[6,102,1008,7860,53340,330372,1918224,10615176, 56602260,293032740,1481004096,7337198232, 35743534008,171641101800,814046047200, 3819148459920,17747499595140,81776562767460, 373968175442400,1698587342436600,7667851012141320, 34422129328312440] |