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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 69 |
| 3 | 420 |
| 4 | 1796 |
| 5 | 12073 |
| 6 | 101397 |
| 7 | 1139211 |
| 8 | 5440508 |
| 9 | 320620306 |
| 10 | 2058187481 |
| 11 | 36451609409 |
| 12 | 54594153615 |
| 13 | 4100904808215 |
[1,7,69,420,1796,12073,101397,1139211,5440508, 320620306,2058187481,36451609409,54594153615, 4100904808215] |