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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 53 |
| 3 | 108 |
| 4 | 2861 |
| 5 | 5830 |
| 6 | 154441 |
| 7 | 314712 |
| 8 | 8336953 |
| 9 | 16988618 |
| 10 | 450041021 |
| 11 | 917070660 |
| 12 | 24293878181 |
| 13 | 49504827022 |
| 14 | 1311419380753 |
| 15 | 2672343588528 |
| 16 | 70792352682481 |
| 17 | 144257048953490 |
| 18 | 3821475625473221 |
| 19 | 7787208299899932 |
| 20 | 206288891422871453 |
| 21 | 420364991145642838 |
[1,2,53,108,2861,5830,154441,314712,8336953, 16988618,450041021,917070660,24293878181, 49504827022,1311419380753,2672343588528, 70792352682481,144257048953490,3821475625473221, 7787208299899932,206288891422871453, 420364991145642838] |