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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 8 |
| 4 | 62 |
| 5 | 898 |
| 6 | 29446 |
| 7 | 1807682 |
| 8 | 188719562 |
| 9 | 33264404940 |
| 10 | 9945976161290 |
[0,2,8,62,898,29446,1807682,188719562,33264404940, 9945976161290] |