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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 54 |
| 5 | 280 |
| 6 | 1695 |
| 7 | 11886 |
| 8 | 95116 |
| 9 | 856080 |
| 10 | 8560845 |
| 11 | 94169350 |
| 12 | 1130032266 |
| 13 | 14690419536 |
| 14 | 205665873595 |
| 15 | 3084988104030 |
| 16 | 49359809664600 |
| 17 | 839116764298336 |
| 18 | 15104101757370201 |
| 19 | 286977933390033990 |
| 20 | 5739558667800679990 |
| 21 | 120530732023814280000 |
| 22 | 2651676104523914160231 |
[1,1,3,12,54,280,1695,11886,95116,856080,8560845, 94169350,1130032266,14690419536,205665873595, 3084988104030,49359809664600,839116764298336, 15104101757370201,286977933390033990, 5739558667800679990,120530732023814280000, 2651676104523914160231] |