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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 94 |
| 6 | 512 |
| 7 | 3485 |
| 8 | 29515 |
| 9 | 314474 |
| 10 | 4255727 |
| 11 | 73831813 |
| 12 | 1653083021 |
| 13 | 47941962135 |
| 14 | 1803010446411 |
| 15 | 87882300251730 |
| 16 | 5543501326580737 |
[1,1,2,6,21,94,512,3485,29515,314474,4255727, 73831813,1653083021,47941962135,1803010446411, 87882300251730,5543501326580737] |