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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 67 |
| 5 | 421 |
| 6 | 3115 |
| 7 | 26349 |
| 8 | 250867 |
| 9 | 2655541 |
| 10 | 30929019 |
| 11 | 393019837 |
| 12 | 5410699075 |
| 13 | 80221867909 |
| 14 | 1274393162827 |
| 15 | 21594697199757 |
| 16 | 388796268801427 |
| 17 | 7411769447027413 |
| 18 | 149143210226032923 |
| 19 | 3159088788867736669 |
[1,1,3,13,67,421,3115,26349,250867,2655541, 30929019,393019837,5410699075,80221867909, 1274393162827,21594697199757,388796268801427, 7411769447027413,149143210226032923, 3159088788867736669] |