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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 715 |
| 7 | 4970 |
| 8 | 39480 |
| 9 | 352800 |
| 10 | 3502800 |
| 11 | 38255900 |
| 12 | 455795100 |
| 13 | 5883052500 |
| 14 | 81774966000 |
| 15 | 1217871018000 |
| 16 | 19346879737625 |
| 17 | 326549862671250 |
| 18 | 5835951345093750 |
| 19 | 110091785625495000 |
| 20 | 2186122850020215000 |
| 21 | 45580964489553559375 |
| 22 | 995625115672520581250 |
[1,1,2,6,24,120,715,4970,39480,352800,3502800, 38255900,455795100,5883052500,81774966000, 1217871018000,19346879737625,326549862671250, 5835951345093750,110091785625495000, 2186122850020215000,45580964489553559375, 995625115672520581250] |