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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 46 |
| 5 | 1372 |
| 6 | 475499108 |
| 7 | 1038397981840994509577948 |
| 8 | 10825608503765473087803384381127710579846422820261084889808 |
[2,4,10,46,1372,475499108, 1038397981840994509577948, 10825608503765473087803384381127710579846422820261\ 084889808] |