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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 16 |
| 4 | 81 |
| 5 | 393 |
| 6 | 1777 |
| 7 | 7633 |
| 8 | 31745 |
| 9 | 129537 |
| 10 | 523009 |
| 11 | 2099969 |
| 12 | 8409089 |
| 13 | 33634305 |
| 14 | 134475777 |
| 15 | 537628673 |
| 16 | 2149580801 |
| 17 | 8595505153 |
| 18 | 34374090753 |
| 19 | 137475063809 |
| 20 | 549844942849 |
| 21 | 2199239786497 |
| 22 | 8796612067329 |
| 23 | 35185602068481 |
| 24 | 140740374036481 |
| 25 | 562956664307713 |
[2,4,16,81,393,1777,7633,31745,129537,523009, 2099969,8409089,33634305,134475777,537628673, 2149580801,8595505153,34374090753,137475063809, 549844942849,2199239786497,8796612067329, 35185602068481,140740374036481,562956664307713] |