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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 216 |
| 3 | 143856 |
| 4 | 2805425280 |
| 5 | 1656812779036416 |
| 6 | 30688414550520167402496 |
[6,216,143856,2805425280,1656812779036416, 30688414550520167402496] |