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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 33 |
| 3 | 410 |
| 4 | 6796 |
| 5 | 140824 |
| 6 | 3501782 |
| 7 | 101589732 |
| 8 | 3368237928 |
| 9 | 125634319104 |
| 10 | 5206805098752 |
| 11 | 237370661584704 |
| 12 | 11805144854303760 |
| 13 | 636030155604374400 |
| 14 | 36903603627294958416 |
| 15 | 2294156656214759133024 |
| 16 | 152126925169297299197184 |
| 17 | 10718105879980375520103936 |
| 18 | 799564645068022035991527552 |
[1,4,33,410,6796,140824,3501782,101589732, 3368237928,125634319104,5206805098752, 237370661584704,11805144854303760, 636030155604374400,36903603627294958416, 2294156656214759133024,152126925169297299197184, 10718105879980375520103936, 799564645068022035991527552] |