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| n | a(n) |
|---|---|
| 1 | 5 |
| 2 | 10 |
| 3 | 120 |
| 4 | 280840 |
| 5 | 3691654113991480 |
| 6 | 8385167839605753859676710992399730619003333960 |
[5,10,120,280840,3691654113991480, 8385167839605753859676710992399730619003333960] |