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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 9 |
| 4 | 54 |
| 5 | 90 |
| 6 | 540 |
| 7 | 945 |
| 8 | 5670 |
| 9 | 10206 |
| 10 | 61236 |
| 11 | 112266 |
| 12 | 673596 |
| 13 | 1250964 |
| 14 | 7505784 |
| 15 | 14073345 |
| 16 | 84440070 |
| 17 | 159497910 |
| 18 | 956987460 |
| 19 | 1818276174 |
| 20 | 10909657044 |
| 21 | 20827527084 |
| 22 | 124965162504 |
| 23 | 239516561466 |
| 24 | 1437099368796 |
| 25 | 2763652632300 |
[1,1,6,9,54,90,540,945,5670,10206,61236,112266, 673596,1250964,7505784,14073345,84440070, 159497910,956987460,1818276174,10909657044, 20827527084,124965162504,239516561466, 1437099368796,2763652632300] |