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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 54 |
| 5 | 448 |
| 6 | 4650 |
| 7 | 53611 |
| 8 | 655033 |
| 9 | 8259635 |
| 10 | 106371085 |
| 11 | 1391032357 |
| 12 | 18412269694 |
[1,2,9,54,448,4650,53611,655033,8259635,106371085, 1391032357,18412269694] |