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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 256 |
| 3 | 257984 |
| 4 | 2868497664 |
| 5 | 322730734532144 |
| 6 | 372006541021912021312 |
[4,256,257984,2868497664,322730734532144, 372006541021912021312] |