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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 17 |
| 4 | 112 |
| 5 | 761 |
| 6 | 6992 |
| 7 | 65267 |
| 8 | 749264 |
| 9 | 8952097 |
| 10 | 123035312 |
| 11 | 1765177435 |
| 12 | 28465913320 |
| 13 | 475981018033 |
| 14 | 8737060100680 |
| 15 | 167186734385795 |
| 16 | 3446660462332576 |
| 17 | 73894280818392641 |
| 18 | 1691674707666258848 |
| 19 | 40160865451008020651 |
| 20 | 1009283508170762388536 |
[1,1,4,17,112,761,6992,65267,749264,8952097, 123035312,1765177435,28465913320,475981018033, 8737060100680,167186734385795,3446660462332576, 73894280818392641,1691674707666258848, 40160865451008020651,1009283508170762388536] |