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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 9 |
| 3 | 55 |
| 4 | 345 |
| 5 | 2251 |
| 6 | 15183 |
| 7 | 104959 |
| 8 | 739161 |
| 9 | 5280931 |
| 10 | 38165259 |
| 11 | 278415919 |
| 12 | 2046924399 |
| 13 | 15148345759 |
| 14 | 112738423359 |
| 15 | 843126957055 |
| 16 | 6332299624281 |
| 17 | 47737325577619 |
| 18 | 361077477684435 |
| 19 | 2739270870994735 |
| 20 | 20836827035351595 |
[1,9,55,345,2251,15183,104959,739161,5280931, 38165259,278415919,2046924399,15148345759, 112738423359,843126957055,6332299624281, 47737325577619,361077477684435,2739270870994735, 20836827035351595] |