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| n | a(n) |
|---|---|
| 1 | 81 |
| 2 | 399 |
| 3 | 1620 |
| 4 | 6462 |
| 5 | 26481 |
| 6 | 110769 |
| 7 | 469617 |
| 8 | 2009553 |
| 9 | 8655441 |
| 10 | 37451697 |
| 11 | 162572721 |
| 12 | 707284113 |
| 13 | 3081856785 |
| 14 | 13442980209 |
| 15 | 58681197681 |
| 16 | 256284824145 |
| 17 | 1119691708881 |
| 18 | 4893034223409 |
| 19 | 21386003380017 |
| 20 | 93482466850833 |
| 21 | 408662174944401 |
[81,399,1620,6462,26481,110769,469617,2009553, 8655441,37451697,162572721,707284113,3081856785, 13442980209,58681197681,256284824145, 1119691708881,4893034223409,21386003380017, 93482466850833,408662174944401] |