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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 26 |
| 3 | 163 |
| 4 | 1125 |
| 5 | 7546 |
| 6 | 51055 |
| 7 | 344525 |
| 8 | 2326760 |
| 9 | 15709977 |
| 10 | 106079739 |
| 11 | 716273960 |
| 12 | 4836475953 |
| 13 | 32657123299 |
| 14 | 220509407586 |
| 15 | 1488936665619 |
| 16 | 10053686907525 |
| 17 | 67885102598386 |
| 18 | 458377829683919 |
| 19 | 3095086053853821 |
| 20 | 20898824215523616 |
[1,3,26,163,1125,7546,51055,344525,2326760, 15709977,106079739,716273960,4836475953, 32657123299,220509407586,1488936665619, 10053686907525,67885102598386,458377829683919, 3095086053853821,20898824215523616] |