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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 48 |
| 5 | 24827831185072145341724578094746750077042972709355520000000000 |
[1,2,4,48, 24827831185072145341724578094746750077042972709355\ 520000000000] |