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| n | a(n) |
|---|---|
| 1 | 18 |
| 2 | 324 |
| 3 | 1526 |
| 4 | 7305 |
| 5 | 41938 |
| 6 | 237576 |
| 7 | 1413961 |
| 8 | 8384076 |
| 9 | 50497372 |
| 10 | 304338351 |
| 11 | 1845174892 |
| 12 | 11203596798 |
| 13 | 68215344617 |
| 14 | 415886615986 |
| 15 | 2539409090804 |
| 16 | 15520995658437 |
| 17 | 94955670400794 |
| 18 | 581344596875918 |
| 19 | 3561439696930289 |
[18,324,1526,7305,41938,237576,1413961,8384076, 50497372,304338351,1845174892,11203596798, 68215344617,415886615986,2539409090804, 15520995658437,94955670400794,581344596875918, 3561439696930289] |