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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 3 |
| 6 | 9 |
| 7 | 19 |
| 8 | 69 |
| 9 | 389 |
| 10 | 2287 |
| 11 | 15081 |
| 12 | 141721 |
| 13 | 1694175 |
| 14 | 23795099 |
| 15 | 418616469 |
| 16 | 9434924199 |
| 17 | 264113682081 |
| 18 | 9153093458787 |
| 19 | 397472720900369 |
| 20 | 21616544571284115 |
| 21 | 1466493314737915869 |
| 22 | 124160358455186794957 |
[1,1,1,1,3,9,19,69,389,2287,15081,141721,1694175, 23795099,418616469,9434924199,264113682081, 9153093458787,397472720900369,21616544571284115, 1466493314737915869,124160358455186794957] |