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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 20 |
| 3 | 519 |
| 4 | 2143067 |
| 5 | 18287805708761 |
| 6 | 18106009499053689257383057825 |
| 7 | 700601920425487669158589840746065001284609234708224745400 |
[4,20,519,2143067,18287805708761, 18106009499053689257383057825, 70060192042548766915858984074606500128460923470822\ 4745400] |