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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 540 |
| 4 | 1360800 |
| 5 | 154314720000 |
| 6 | 1154953090368000000 |
| 7 | 786615912769073587200000000 |
| 8 | 64289841661815089567953305600000000000 |
| 9 | 803921077736369993656026249310037606400000000000000 |
[1,1,6,540,1360800,154314720000, 1154953090368000000,786615912769073587200000000, 64289841661815089567953305600000000000, 80392107773636999365602624931003760640000000000000\ 0] |