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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 12 |
| 2 | 99 |
| 3 | 686 |
| 4 | 4305 |
| 5 | 25368 |
| 6 | 143263 |
| 7 | 785202 |
| 8 | 4211229 |
| 9 | 22226204 |
| 10 | 115899147 |
| 11 | 598832598 |
| 12 | 3072304873 |
| 13 | 15676477920 |
| 14 | 79649367351 |
| 15 | 403336249274 |
| 16 | 2037103422837 |
| 17 | 10267399442916 |
| 18 | 51665107485475 |
[1,12,99,686,4305,25368,143263,785202,4211229, 22226204,115899147,598832598,3072304873, 15676477920,79649367351,403336249274, 2037103422837,10267399442916,51665107485475] |