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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 17 |
| 4 | 135 |
| 5 | 1353 |
| 6 | 16251 |
| 7 | 226857 |
| 8 | 3605775 |
| 9 | 64288209 |
| 10 | 1270969971 |
| 11 | 27603549057 |
| 12 | 653517822615 |
| 13 | 16755529944729 |
| 14 | 462601460800491 |
| 15 | 13685474246611737 |
| 16 | 431948067953729055 |
| 17 | 14489465807596684449 |
| 18 | 514794897939436455651 |
[0,1,3,17,135,1353,16251,226857,3605775,64288209, 1270969971,27603549057,653517822615, 16755529944729,462601460800491,13685474246611737, 431948067953729055,14489465807596684449, 514794897939436455651] |