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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 66 |
| 4 | 901 |
| 5 | 13881 |
| 6 | 231008 |
| 7 | 4057660 |
| 8 | 74174927 |
| 9 | 1398295989 |
| 10 | 27012396022 |
| 11 | 532327974882 |
| 12 | 10665521789203 |
| 13 | 227093585071305 |
| 14 | 4455636282185802 |
| 15 | 92567760074841818 |
[1,6,66,901,13881,231008,4057660,74174927, 1398295989,27012396022,532327974882, 10665521789203,227093585071305,4455636282185802, 92567760074841818] |