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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 45 |
| 3 | 405 |
| 4 | 4095 |
| 5 | 40500 |
| 6 | 405450 |
| 7 | 4050000 |
| 8 | 40504500 |
| 9 | 405000000 |
| 10 | 4050045000 |
| 11 | 40500000000 |
| 12 | 405000450000 |
| 13 | 4050000000000 |
| 14 | 40500004500000 |
| 15 | 405000000000000 |
| 16 | 4050000045000000 |
| 17 | 40500000000000000 |
| 18 | 405000000450000000 |
| 19 | 4050000000000000000 |
| 20 | 40500000004500000000 |
| 21 | 405000000000000000000 |
[4,45,405,4095,40500,405450,4050000,40504500, 405000000,4050045000,40500000000,405000450000, 4050000000000,40500004500000,405000000000000, 4050000045000000,40500000000000000, 405000000450000000,4050000000000000000, 40500000004500000000,405000000000000000000] |