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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 31 |
| 3 | 211 |
| 4 | 1333 |
| 5 | 6541 |
| 6 | 45787 |
| 7 | 281263 |
| 8 | 1968841 |
| 9 | 13781887 |
| 10 | 93098053 |
| 11 | 649998793 |
| 12 | 4549991551 |
| 13 | 31849940857 |
| 14 | 215149600483 |
| 15 | 1506047203381 |
| 16 | 10542330423667 |
| 17 | 86982188480467 |
| 18 | 587573558919073 |
| 19 | 4113014912433511 |
| 20 | 28791104387034577 |
| 21 | 247368468304929733 |
[1,7,31,211,1333,6541,45787,281263,1968841, 13781887,93098053,649998793,4549991551, 31849940857,215149600483,1506047203381, 10542330423667,86982188480467,587573558919073, 4113014912433511,28791104387034577, 247368468304929733] |