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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 3 |
| 6 | 15 |
| 7 | 60 |
| 8 | 70 |
| 9 | 140 |
| 10 | 540 |
| 11 | 37800 |
| 12 | 8316 |
| 13 | 207900 |
| 14 | 1351350 |
| 15 | 75675600 |
| 16 | 141891750 |
| 17 | 11176704 |
| 18 | 308756448000 |
| 19 | 222304642560 |
| 20 | 15084957888000 |
| 21 | 234654900480000 |
| 22 | 1267136462592000 |
| 23 | 139385010885120000 |
| 24 | 213723683357184000 |
[1,1,1,2,6,3,15,60,70,140,540,37800,8316,207900, 1351350,75675600,141891750,11176704,308756448000, 222304642560,15084957888000,234654900480000, 1267136462592000,139385010885120000, 213723683357184000] |