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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 139 |
| 4 | 1218 |
| 5 | 11511 |
| 6 | 114398 |
| 7 | 1178421 |
| 8 | 12469626 |
| 9 | 134734092 |
| 10 | 1480317468 |
| 11 | 16487870031 |
| 12 | 185744716414 |
| 13 | 2112756042468 |
| 14 | 24230663513604 |
| 15 | 279889210974003 |
| 16 | 3253295301115290 |
| 17 | 38023971948455859 |
| 18 | 446603044829013514 |
| 19 | 5268557500949993964 |
| 20 | 62398899992129490756 |
[1,3,18,139,1218,11511,114398,1178421,12469626, 134734092,1480317468,16487870031,185744716414, 2112756042468,24230663513604,279889210974003, 3253295301115290,38023971948455859, 446603044829013514,5268557500949993964, 62398899992129490756] |