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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 6 |
| 3 | 18 |
| 4 | 51 |
| 5 | 147 |
| 6 | 423 |
| 7 | 1218 |
| 8 | 3507 |
| 9 | 10098 |
| 10 | 29076 |
| 11 | 83721 |
| 12 | 241065 |
| 13 | 694119 |
| 14 | 1998636 |
| 15 | 5754843 |
| 16 | 16570410 |
| 17 | 47712594 |
| 18 | 137382939 |
| 19 | 395578407 |
| 20 | 1139022627 |
| 21 | 3279684942 |
| 22 | 9443476419 |
| 23 | 27191406630 |
| 24 | 78294534948 |
| 25 | 225440128425 |
| 26 | 649128978645 |
| 27 | 1869092400987 |
| 28 | 5381837074536 |
[1,3,6,18,51,147,423,1218,3507,10098,29076,83721, 241065,694119,1998636,5754843,16570410,47712594, 137382939,395578407,1139022627,3279684942, 9443476419,27191406630,78294534948,225440128425, 649128978645,1869092400987,5381837074536] |