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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 32 |
| 3 | 252 |
| 4 | 1985 |
| 5 | 15647 |
| 6 | 123337 |
| 7 | 972168 |
| 8 | 7662841 |
| 9 | 60400282 |
| 10 | 476088932 |
| 11 | 3752642337 |
| 12 | 29579189147 |
| 13 | 233149966025 |
| 14 | 1837741608616 |
| 15 | 14485501658565 |
| 16 | 114178052735590 |
| 17 | 899977648952776 |
| 18 | 7093830637396745 |
| 19 | 55915203194889879 |
| 20 | 440736480491065049 |
[4,32,252,1985,15647,123337,972168,7662841, 60400282,476088932,3752642337,29579189147, 233149966025,1837741608616,14485501658565, 114178052735590,899977648952776,7093830637396745, 55915203194889879,440736480491065049] |