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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 11 |
| 5 | 32 |
| 6 | 128 |
| 7 | 608 |
| 8 | 3689 |
| 9 | 27238 |
| 10 | 244922 |
| 11 | 2659678 |
| 12 | 35013106 |
| 13 | 562450090 |
[1,2,4,11,32,128,608,3689,27238,244922,2659678, 35013106,562450090] |