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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 100 |
| 5 | 794 |
| 6 | 10414 |
| 7 | 190428 |
| 8 | 4659387 |
| 9 | 143848365 |
| 10 | 5430367157 |
| 11 | 242216815664 |
| 12 | 12631766954130 |
| 13 | 754181337363809 |
[2,6,18,100,794,10414,190428,4659387,143848365, 5430367157,242216815664,12631766954130, 754181337363809] |