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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 127 |
| 4 | 2165 |
| 5 | 40914 |
| 6 | 824859 |
| 7 | 17383720 |
| 8 | 378373437 |
| 9 | 8440227235 |
| 10 | 191938302578 |
| 11 | 4433259845898 |
| 12 | 103716352560119 |
| 13 | 2452629475989840 |
| 14 | 58529969579982600 |
| 15 | 1407775987050271920 |
| 16 | 34092047564798908045 |
| 17 | 830565580516900384329 |
| 18 | 20342106952028722530603 |
| 19 | 500573735323751221019425 |
| 20 | 12370242700776737398052970 |
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