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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 55 |
| 4 | 529 |
| 5 | 6121 |
| 6 | 82711 |
| 7 | 1273567 |
| 8 | 21945505 |
| 9 | 417540529 |
| 10 | 8680953511 |
| 11 | 195582295591 |
| 12 | 4742407056817 |
| 13 | 123045795823705 |
| 14 | 3399348471640759 |
| 15 | 99573135106176271 |
| 16 | 3081061456572152641 |
| 17 | 100382623544966098657 |
| 18 | 3433727597233037475655 |
| 19 | 123000248740384210119319 |
| 20 | 4603377404407810366309201 |
[1,1,7,55,529,6121,82711,1273567,21945505, 417540529,8680953511,195582295591,4742407056817, 123045795823705,3399348471640759, 99573135106176271,3081061456572152641, 100382623544966098657,3433727597233037475655, 123000248740384210119319, 4603377404407810366309201] |