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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 14 |
| 5 | 60 |
| 6 | 450 |
| 7 | 4964 |
| 8 | 95982 |
| 9 | 3037948 |
| 10 | 170005730 |
| 11 | 16522010532 |
| 12 | 2882717916878 |
| 13 | 902450057292988 |
| 14 | 514768747418386946 |
| 15 | 537142988843543963620 |
| 16 | 1033976171696917695108270 |
| 17 | 3688322935382700002945333884 |
| 18 | 24514290054855626308893309022498 |
[1,1,2,4,14,60,450,4964,95982,3037948,170005730, 16522010532,2882717916878,902450057292988, 514768747418386946,537142988843543963620, 1033976171696917695108270, 3688322935382700002945333884, 24514290054855626308893309022498] |