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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 768 |
| 3 | 1555200 |
| 4 | 20808990720 |
| 5 | 9029615616000000 |
| 6 | 1415988202438656000000 |
| 7 | 536259842454308939366400000 |
| 8 | 7188611938994779905746534400000000 |
| 9 | 503281313253202450261043834781696000000 |
[1,4,768,1555200,20808990720,9029615616000000, 1415988202438656000000, 536259842454308939366400000, 7188611938994779905746534400000000, 503281313253202450261043834781696000000] |