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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 420 |
| 3 | 301612 |
| 4 | 729771318 |
| 5 | 1706069013928 |
| 6 | 2238761872232964 |
| 7 | 1716349328902123738 |
[4,420,301612,729771318,1706069013928, 2238761872232964,1716349328902123738] |