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| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 5 |
| 4 | 30 |
| 5 | 180 |
| 6 | 1028 |
| 7 | 6563 |
| 8 | 41042 |
| 9 | 262143 |
| 10 | 1737014 |
| 11 | 11717093 |
| 12 | 80135236 |
| 13 | 555094742 |
| 14 | 3884459568 |
| 15 | 27420679509 |
| 16 | 195037451422 |
[2,5,30,180,1028,6563,41042,262143,1737014, 11717093,80135236,555094742,3884459568, 27420679509,195037451422] |