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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 33 |
| 7 | 261 |
| 8 | 3125 |
| 9 | 54281 |
| 10 | 1360227 |
| 11 | 49213679 |
| 12 | 2551724168 |
| 13 | 189734190172 |
| 14 | 20202532257783 |
| 15 | 3077389342754387 |
| 16 | 670727373110373402 |
| 17 | 209089605110085626174 |
| 18 | 93228754516671937710239 |
| 19 | 59465333534426105454885059 |
| 20 | 54262238803939167296498684986 |
[1,1,1,1,2,6,33,261,3125,54281,1360227,49213679, 2551724168,189734190172,20202532257783, 3077389342754387,670727373110373402, 209089605110085626174,93228754516671937710239, 59465333534426105454885059, 54262238803939167296498684986] |