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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 5 |
| 6 | 17 |
| 7 | 51 |
| 8 | 255 |
| 9 | 1303 |
| 10 | 6487 |
| 11 | 45597 |
| 12 | 373491 |
| 13 | 4375333 |
| 14 | 54687233 |
| 15 | 1001558187 |
| 16 | 19226580191 |
[1,1,1,1,5,17,51,255,1303,6487,45597,373491, 4375333,54687233,1001558187,19226580191] |