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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 3 |
| 3 | 6 |
| 4 | 15 |
| 5 | 48 |
| 6 | 232 |
| 7 | 1544 |
| 8 | 14959 |
| 9 | 203333 |
| 10 | 3919437 |
| 11 | 105126522 |
[1,2,3,6,15,48,232,1544,14959,203333,3919437, 105126522] |