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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 8 |
| 3 | 20 |
| 4 | 92 |
| 5 | 2744 |
| 6 | 950998216 |
| 7 | 2076795963681989019155896 |
| 8 | 21651217007530946175606768762255421159692845640522169779616 |
[4,8,20,92,2744,950998216, 2076795963681989019155896, 21651217007530946175606768762255421159692845640522\ 169779616] |