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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 32 |
| 3 | 228 |
| 4 | 1651 |
| 5 | 11965 |
| 6 | 86775 |
| 7 | 629440 |
| 8 | 4566023 |
| 9 | 33122989 |
| 10 | 240283124 |
| 11 | 1743081647 |
| 12 | 12644813016 |
| 13 | 91729105941 |
| 14 | 665429316237 |
| 15 | 4827215711786 |
| 16 | 35018011778092 |
| 17 | 254030734032018 |
| 18 | 1842812043966813 |
| 19 | 13368288852038965 |
| 20 | 96977414177346279 |
[4,32,228,1651,11965,86775,629440,4566023, 33122989,240283124,1743081647,12644813016, 91729105941,665429316237,4827215711786, 35018011778092,254030734032018,1842812043966813, 13368288852038965,96977414177346279] |