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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 60 |
| 5 | 375 |
| 6 | 2613 |
| 7 | 19074 |
| 8 | 143660 |
| 9 | 1101860 |
| 10 | 8562292 |
| 11 | 67206242 |
| 12 | 531804577 |
| 13 | 4236708679 |
[1,3,12,60,375,2613,19074,143660,1101860,8562292, 67206242,531804577,4236708679] |