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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 33 |
| 3 | 341 |
| 4 | 3860 |
| 5 | 45801 |
| 6 | 558967 |
| 7 | 6949276 |
| 8 | 87529800 |
| 9 | 1113178232 |
| 10 | 14262575360 |
| 11 | 183817376373 |
| 12 | 2380397391739 |
| 13 | 30947782216312 |
| 14 | 403696062660177 |
| 15 | 5280951542877725 |
| 16 | 69252255466431356 |
| 17 | 910088352234643128 |
| 18 | 11982557663480438404 |
| 19 | 158029913929209576448 |
[1,4,33,341,3860,45801,558967,6949276,87529800, 1113178232,14262575360,183817376373,2380397391739, 30947782216312,403696062660177,5280951542877725, 69252255466431356,910088352234643128, 11982557663480438404,158029913929209576448] |