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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 54 |
| 5 | 214 |
| 6 | 919 |
| 7 | 3984 |
| 8 | 17772 |
| 9 | 80080 |
| 10 | 366595 |
| 11 | 1691770 |
| 12 | 7877604 |
| 13 | 36926470 |
| 14 | 174112034 |
| 15 | 824899323 |
| 16 | 3925561729 |
| 17 | 18748361538 |
| 18 | 89833469739 |
| 19 | 431690857897 |
| 20 | 2079682186282 |
| 21 | 10041508850305 |
| 22 | 48584193517259 |
| 23 | 235491620594297 |
| 24 | 1143330270479493 |
| 25 | 5559375459322033 |
| 26 | 27068814795311369 |
| 27 | 131963539891053946 |
[1,1,4,13,54,214,919,3984,17772,80080,366595, 1691770,7877604,36926470,174112034,824899323, 3925561729,18748361538,89833469739,431690857897, 2079682186282,10041508850305,48584193517259, 235491620594297,1143330270479493,5559375459322033, 27068814795311369,131963539891053946] |