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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 90 |
| 4 | 11016 |
| 5 | 7083180 |
| 6 | 23491810780 |
| 7 | 398328574277322 |
| 8 | 34356415364024198698 |
| 9 | 15026792073190842661982128 |
| 10 | 33259034071925704355191308972010 |
[1,4,90,11016,7083180,23491810780,398328574277322, 34356415364024198698,15026792073190842661982128, 33259034071925704355191308972010] |