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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 83 |
| 4 | 483 |
| 5 | 2898 |
| 6 | 17748 |
| 7 | 110295 |
| 8 | 692967 |
| 9 | 4390815 |
| 10 | 28009215 |
| 11 | 179652564 |
| 12 | 1157534420 |
| 13 | 7486680048 |
| 14 | 48579667704 |
| 15 | 316107403839 |
| 16 | 2061920664351 |
| 17 | 13478362911825 |
| 18 | 88272020923485 |
| 19 | 579081767982795 |
| 20 | 3804622827123195 |
[1,3,15,83,483,2898,17748,110295,692967,4390815, 28009215,179652564,1157534420,7486680048, 48579667704,316107403839,2061920664351, 13478362911825,88272020923485,579081767982795, 3804622827123195] |