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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 9 |
| 4 | 56 |
| 5 | 499 |
| 6 | 8000 |
| 7 | 207554 |
| 8 | 9382078 |
| 9 | 732814910 |
| 10 | 101599273769 |
| 11 | 25151730678684 |
| 12 | 11252735518379960 |
| 13 | 9169484084583765409 |
| 14 | 13716523699765295956974 |
| 15 | 37907229783585348802398136 |
| 16 | 194640906178869631364050052914 |
[2,4,9,56,499,8000,207554,9382078,732814910, 101599273769,25151730678684,11252735518379960, 9169484084583765409,13716523699765295956974, 37907229783585348802398136, 194640906178869631364050052914] |