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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 8 |
| 3 | 55 |
| 4 | 559 |
| 5 | 5935 |
| 6 | 67681 |
| 7 | 802125 |
| 8 | 9804610 |
| 9 | 122616851 |
| 10 | 1561658960 |
| 11 | 20184817925 |
| 12 | 264098109360 |
[1,8,55,559,5935,67681,802125,9804610,122616851, 1561658960,20184817925,264098109360] |