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| n | a(n) |
|---|---|
| 3 | 2 |
| 4 | 5 |
| 5 | 21 |
| 6 | 121 |
| 7 | 841 |
| 8 | 6721 |
| 9 | 60481 |
| 10 | 604801 |
| 11 | 6652801 |
| 12 | 79833601 |
| 13 | 1037836801 |
| 14 | 14529715201 |
| 15 | 217945728001 |
| 16 | 3487131648001 |
| 17 | 59281238016001 |
| 18 | 1067062284288001 |
| 19 | 20274183401472001 |
| 20 | 405483668029440001 |
| 21 | 8515157028618240001 |
[2,5,21,121,841,6721,60481,604801,6652801, 79833601,1037836801,14529715201,217945728001, 3487131648001,59281238016001,1067062284288001, 20274183401472001,405483668029440001, 8515157028618240001] |