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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 100 |
| 6 | 518 |
| 7 | 3122 |
| 8 | 20676 |
| 9 | 154524 |
| 10 | 1238952 |
| 11 | 11030448 |
| 12 | 103376832 |
| 13 | 1068000024 |
| 14 | 11407673496 |
| 15 | 134352996744 |
| 16 | 1603035004368 |
| 17 | 21276244952784 |
| 18 | 278535036773856 |
| 19 | 4141886572833888 |
| 20 | 58405909554175776 |
| 21 | 973789956270781056 |
| 22 | 14462380128843907680 |
[1,1,2,6,22,100,518,3122,20676,154524,1238952, 11030448,103376832,1068000024,11407673496, 134352996744,1603035004368,21276244952784, 278535036773856,4141886572833888, 58405909554175776,973789956270781056, 14462380128843907680] |