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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 73 |
| 6 | 241 |
| 7 | 768 |
| 8 | 2415 |
| 9 | 7587 |
| 10 | 23905 |
| 11 | 75507 |
| 12 | 238759 |
| 13 | 755088 |
| 14 | 2387570 |
| 15 | 7548085 |
| 16 | 23860518 |
| 17 | 75425046 |
| 18 | 238427267 |
| 19 | 753705647 |
| 20 | 2382596754 |
| 21 | 7531821990 |
| 22 | 23809446690 |
| 23 | 75265885442 |
| 24 | 237928695207 |
| 25 | 752134317626 |
| 26 | 2377628496399 |
[1,2,6,21,73,241,768,2415,7587,23905,75507,238759, 755088,2387570,7548085,23860518,75425046, 238427267,753705647,2382596754,7531821990, 23809446690,75265885442,237928695207,752134317626, 2377628496399] |