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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 7 |
| 4 | 37 |
| 5 | 241 |
| 6 | 2101 |
| 7 | 18271 |
| 8 | 201097 |
| 9 | 2270017 |
| 10 | 29668681 |
| 11 | 410815351 |
| 12 | 6238931821 |
| 13 | 101560835377 |
| 14 | 1765092183037 |
| 15 | 32838929702671 |
| 16 | 644215775792401 |
| 17 | 13441862819232001 |
| 18 | 293976795292186897 |
| 19 | 6788407001443004647 |
| 20 | 163735077313046119861 |
| 21 | 4142654439686285737201 |
[1,1,1,7,37,241,2101,18271,201097,2270017, 29668681,410815351,6238931821,101560835377, 1765092183037,32838929702671,644215775792401, 13441862819232001,293976795292186897, 6788407001443004647,163735077313046119861, 4142654439686285737201] |