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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 73 |
| 5 | 501 |
| 6 | 3337 |
| 7 | 27637 |
| 8 | 254409 |
| 9 | 2557369 |
| 10 | 27603631 |
| 11 | 313768731 |
| 12 | 3905502745 |
| 13 | 51573777841 |
| 14 | 718307494269 |
| 15 | 10507900625251 |
| 16 | 161239887204721 |
| 17 | 2608009648536417 |
| 18 | 43989477103304155 |
| 19 | 772109936171046001 |
| 20 | 14085074476090366761 |
| 21 | 266890182641557777093 |
[1,1,3,13,73,501,3337,27637,254409,2557369, 27603631,313768731,3905502745,51573777841, 718307494269,10507900625251,161239887204721, 2608009648536417,43989477103304155, 772109936171046001,14085074476090366761, 266890182641557777093] |