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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 15 |
| 3 | 76 |
| 4 | 383 |
| 5 | 1915 |
| 6 | 9576 |
| 7 | 47883 |
| 8 | 239415 |
| 9 | 1197076 |
| 10 | 5985383 |
| 11 | 29926915 |
| 12 | 149634576 |
| 13 | 748172883 |
| 14 | 3740864415 |
| 15 | 18704322076 |
| 16 | 93521610383 |
| 17 | 467608051915 |
| 18 | 2338040259576 |
| 19 | 11690201297883 |
| 20 | 58451006489415 |
| 21 | 292255032447076 |
[3,15,76,383,1915,9576,47883,239415,1197076, 5985383,29926915,149634576,748172883,3740864415, 18704322076,93521610383,467608051915, 2338040259576,11690201297883,58451006489415, 292255032447076] |