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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 30 |
| 4 | 64864800 |
| 5 | 822336494953469303808000000 |
| 6 | 98349960836205821940270184651038804258510922190452164539040399360000000000000 |
[1,1,30,64864800,822336494953469303808000000, 98349960836205821940270184651038804258510922190452\ 164539040399360000000000000] |