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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 45 |
| 6 | 237 |
| 7 | 1591 |
| 8 | 11795 |
| 9 | 99651 |
| 10 | 928507 |
| 11 | 9474043 |
| 12 | 104866399 |
| 13 | 1249073623 |
| 14 | 15914416345 |
| 15 | 215724860511 |
| 16 | 3097002496225 |
| 17 | 46904398032017 |
| 18 | 746831626559889 |
| 19 | 12463977258581151 |
| 20 | 217445976215654257 |
| 21 | 3956098180940284169 |
| 22 | 74897945785223884653 |
[1,1,1,3,9,45,237,1591,11795,99651,928507,9474043, 104866399,1249073623,15914416345,215724860511, 3097002496225,46904398032017,746831626559889, 12463977258581151,217445976215654257, 3956098180940284169,74897945785223884653] |