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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 64 |
| 3 | 8704 |
| 4 | 15106048 |
| 5 | 354003288064 |
| 6 | 115737559589453824 |
| 7 | 542277543422445827915776 |
[4,64,8704,15106048,354003288064, 115737559589453824,542277543422445827915776] |