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| n | a(n) |
|---|---|
| 1 | 20 |
| 2 | 21 |
| 3 | 283 |
| 4 | 1605 |
| 5 | 9817 |
| 6 | 52704 |
| 7 | 279458 |
| 8 | 1485408 |
| 9 | 7898483 |
| 10 | 41071878 |
| 11 | 205411559 |
| 12 | 983354244 |
| 13 | 4524348747 |
| 14 | 20138886182 |
| 15 | 87167200173 |
| 16 | 367779504535 |
| 17 | 1513868192185 |
| 18 | 6081577731882 |
| 19 | 23858481057510 |
| 20 | 91492233259175 |
| 21 | 343337879987807 |
[20,21,283,1605,9817,52704,279458,1485408,7898483, 41071878,205411559,983354244,4524348747, 20138886182,87167200173,367779504535, 1513868192185,6081577731882,23858481057510, 91492233259175,343337879987807] |