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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 7 |
| 3 | 31 |
| 4 | 127 |
| 5 | 8191 |
| 6 | 131071 |
| 7 | 524287 |
| 8 | 2147483647 |
| 9 | 2305843009213693951 |
[3,7,31,127,8191,131071,524287,2147483647, 2305843009213693951] |