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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 108 |
| 4 | 729 |
| 5 | 5103 |
| 6 | 37179 |
| 7 | 277749 |
| 8 | 2119203 |
| 9 | 16435305 |
| 10 | 129199212 |
| 11 | 1027098306 |
| 12 | 8243181351 |
| 13 | 66698502705 |
| 14 | 543507899346 |
| 15 | 4456368744804 |
| 16 | 36738955831707 |
| 17 | 304354824214977 |
| 18 | 2532328310730798 |
| 19 | 21152326520189628 |
| 20 | 177310026608555619 |
| 21 | 1491097815365481477 |
[1,3,18,108,729,5103,37179,277749,2119203, 16435305,129199212,1027098306,8243181351, 66698502705,543507899346,4456368744804, 36738955831707,304354824214977,2532328310730798, 21152326520189628,177310026608555619, 1491097815365481477] |