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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 4 |
| 4 | 19 |
| 5 | 179 |
| 6 | 16142 |
| 7 | 489996794 |
| 8 | 1392195548399980209 |
| 9 | 789204635842035039135545297410259321 |
[1,4,19,179,16142,489996794,1392195548399980209, 789204635842035039135545297410259321] |