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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 84 |
| 6 | 360 |
| 7 | 1650 |
| 8 | 7865 |
| 9 | 39039 |
| 10 | 198744 |
| 11 | 1039584 |
| 12 | 5534928 |
| 13 | 30046752 |
| 14 | 165257136 |
| 15 | 922280634 |
| 16 | 5199131025 |
| 17 | 29644168125 |
| 18 | 170375955750 |
| 19 | 988180543350 |
| 20 | 5768664340725 |
| 21 | 33927954699600 |
| 22 | 200617471267200 |
| 23 | 1193673954039840 |
[1,1,2,6,21,84,360,1650,7865,39039,198744,1039584, 5534928,30046752,165257136,922280634,5199131025, 29644168125,170375955750,988180543350, 5768664340725,33927954699600,200617471267200, 1193673954039840] |