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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 19 |
| 3 | 556 |
| 4 | 2945786 |
| 5 | 1201330980739424 |
| 6 | 1846150007042109336331740689419264 |
| 7 | 44872306407070078313805671235110493948692333391216774983943586135973888 |
[4,19,556,2945786,1201330980739424, 1846150007042109336331740689419264, 44872306407070078313805671235110493948692333391216\ 774983943586135973888] |