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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 19 |
| 5 | 55 |
| 6 | 177 |
| 7 | 543 |
| 8 | 1785 |
| 9 | 5893 |
| 10 | 20137 |
| 11 | 68129 |
| 12 | 238041 |
| 13 | 829015 |
| 14 | 2944829 |
| 15 | 10423247 |
| 16 | 37540189 |
| 17 | 134848851 |
| 18 | 490691205 |
| 19 | 1781665117 |
| 20 | 6540487427 |
| 21 | 23967631953 |
| 22 | 88616165037 |
| 23 | 327138472525 |
| 24 | 1216949007955 |
| 25 | 4521327136295 |
| 26 | 16907134893315 |
| 27 | 63150657774413 |
| 28 | 237215276913281 |
[1,1,3,7,19,55,177,543,1785,5893,20137,68129, 238041,829015,2944829,10423247,37540189,134848851, 490691205,1781665117,6540487427,23967631953, 88616165037,327138472525,1216949007955, 4521327136295,16907134893315,63150657774413, 237215276913281] |