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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 20 |
| 3 | 1635 |
| 4 | 342601 |
| 5 | 146163330 |
| 6 | 110811673197 |
| 7 | 136132704627644 |
| 8 | 253516051052571276 |
[1,20,1635,342601,146163330,110811673197, 136132704627644,253516051052571276] |