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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 12 |
| 6 | 34 |
| 7 | 125 |
| 8 | 450 |
| 9 | 1780 |
| 10 | 7021 |
| 11 | 28521 |
| 12 | 115553 |
| 13 | 472578 |
| 14 | 1927634 |
| 15 | 7890893 |
| 16 | 32221475 |
| 17 | 131812746 |
| 18 | 538059836 |
| 19 | 2198986587 |
| 20 | 8970624060 |
| 21 | 36628143111 |
| 22 | 149328243327 |
| 23 | 609238673619 |
[1,1,2,4,12,34,125,450,1780,7021,28521,115553, 472578,1927634,7890893,32221475,131812746, 538059836,2198986587,8970624060,36628143111, 149328243327,609238673619] |