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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 54 |
| 4 | 480 |
| 5 | 5290 |
| 6 | 70080 |
| 7 | 1083614 |
| 8 | 19145728 |
| 9 | 380552274 |
| 10 | 8404669440 |
| 11 | 204182993542 |
| 12 | 5411361939456 |
| 13 | 155365918497530 |
| 14 | 4803852288901120 |
| 15 | 159142710151610670 |
| 16 | 5623576097060290560 |
| 17 | 211138456468635968674 |
| 18 | 8393550198348236193792 |
| 19 | 352212802264773650385110 |
[1,2,8,54,480,5290,70080,1083614,19145728, 380552274,8404669440,204182993542,5411361939456, 155365918497530,4803852288901120, 159142710151610670,5623576097060290560, 211138456468635968674,8393550198348236193792, 352212802264773650385110] |