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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 20 |
| 5 | 63 |
| 6 | 233 |
| 7 | 966 |
| 8 | 4454 |
| 9 | 22404 |
| 10 | 121616 |
| 11 | 706361 |
| 12 | 4361910 |
| 13 | 28491982 |
| 14 | 196018395 |
| 15 | 1414922459 |
| 16 | 10677120529 |
| 17 | 83924901635 |
| 18 | 684582037213 |
| 19 | 5772723290503 |
| 20 | 50123602905429 |
| 21 | 446382776341382 |
| 22 | 4062023996661972 |
| 23 | 37638652689027910 |
| 24 | 354017801203414670 |
[1,1,3,7,20,63,233,966,4454,22404,121616,706361, 4361910,28491982,196018395,1414922459,10677120529, 83924901635,684582037213,5772723290503, 50123602905429,446382776341382,4062023996661972, 37638652689027910,354017801203414670] |