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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 27 |
| 4 | 312 |
| 5 | 4140 |
| 6 | 58806 |
| 7 | 876492 |
| 8 | 13524300 |
| 9 | 214168536 |
| 10 | 3460901967 |
| 11 | 56842100298 |
| 12 | 946076020551 |
| 13 | 15922147355532 |
| 14 | 270496012834332 |
| 15 | 4632597495220104 |
| 16 | 79896692540736729 |
| 17 | 1386424262414762046 |
| 18 | 24188862129358547349 |
| 19 | 424059773742487363743 |
| 20 | 7466416997545500727257 |
| 21 | 131972899585564980561060 |
[1,3,27,312,4140,58806,876492,13524300,214168536, 3460901967,56842100298,946076020551, 15922147355532,270496012834332,4632597495220104, 79896692540736729,1386424262414762046, 24188862129358547349,424059773742487363743, 7466416997545500727257,131972899585564980561060] |