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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 31 |
| 4 | 265 |
| 5 | 2621 |
| 6 | 31621 |
| 7 | 426595 |
| 8 | 6574961 |
| 9 | 111673945 |
| 10 | 2092318021 |
| 11 | 42552808871 |
| 12 | 937495160185 |
| 13 | 22150499622421 |
| 14 | 559765402811525 |
| 15 | 15039597200385451 |
| 16 | 428293292251548001 |
| 17 | 12875707199330296625 |
| 18 | 407547173842501629061 |
[1,1,5,31,265,2621,31621,426595,6574961,111673945, 2092318021,42552808871,937495160185, 22150499622421,559765402811525,15039597200385451, 428293292251548001,12875707199330296625, 407547173842501629061] |