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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 21 |
| 3 | 1531 |
| 4 | 44782251 |
| 5 | 96076794891512491 |
| 6 | 886151997189943927518995693301312171 |
| 7 | 150770949527755462791108053396729046910357127815416821444325531778055580331 |
[4,21,1531,44782251,96076794891512491, 886151997189943927518995693301312171, 15077094952775546279110805339672904691035712781541\ 6821444325531778055580331] |