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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 15 |
| 5 | 89 |
| 6 | 904 |
| 7 | 10469 |
| 8 | 202299 |
| 9 | 6253788 |
| 10 | 295345323 |
| 11 | 20297903190 |
| 12 | 2062672356086 |
| 13 | 313264131593508 |
[1,1,1,15,89,904,10469,202299,6253788,295345323, 20297903190,2062672356086,313264131593508] |