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| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 6 |
| 4 | 34 |
| 5 | 221 |
| 6 | 1100 |
| 7 | 6711 |
| 8 | 40137 |
| 9 | 256224 |
| 10 | 1690933 |
| 11 | 11342919 |
| 12 | 77426134 |
| 13 | 536305675 |
| 14 | 3750315161 |
| 15 | 26444298871 |
| 16 | 187832060390 |
[2,6,34,221,1100,6711,40137,256224,1690933, 11342919,77426134,536305675,3750315161, 26444298871,187832060390] |