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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 9 |
| 2 | 51 |
| 3 | 279 |
| 4 | 1551 |
| 5 | 8799 |
| 6 | 50751 |
| 7 | 296319 |
| 8 | 1745151 |
| 9 | 10339839 |
| 10 | 61514751 |
| 11 | 366991359 |
| 12 | 2193559551 |
| 13 | 13127802879 |
| 14 | 78632599551 |
| 15 | 471258726399 |
| 16 | 2825404874751 |
| 17 | 16943839313919 |
| 18 | 101628676145151 |
| 19 | 609634617917439 |
| 20 | 3657257951690751 |
[1,9,51,279,1551,8799,50751,296319,1745151, 10339839,61514751,366991359,2193559551, 13127802879,78632599551,471258726399, 2825404874751,16943839313919,101628676145151, 609634617917439,3657257951690751] |