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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 75 |
| 5 | 557 |
| 6 | 5179 |
| 7 | 58589 |
| 8 | 784715 |
| 9 | 12154061 |
| 10 | 213593563 |
| 11 | 4195613373 |
| 12 | 91031201643 |
| 13 | 2160916171181 |
| 14 | 55687501548539 |
| 15 | 1547866851663261 |
| 16 | 46150908197995403 |
| 17 | 1469089501918434957 |
| 18 | 49722765216242122267 |
| 19 | 1782934051704982201469 |
| 20 | 67514992620138056010667 |
[1,1,3,13,75,557,5179,58589,784715,12154061, 213593563,4195613373,91031201643,2160916171181, 55687501548539,1547866851663261,46150908197995403, 1469089501918434957,49722765216242122267, 1782934051704982201469,67514992620138056010667] |