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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 8 |
| 3 | 84 |
| 4 | 992 |
| 5 | 12514 |
| 6 | 164688 |
| 7 | 2232200 |
| 8 | 30920128 |
| 9 | 435506703 |
| 10 | 6215660600 |
| 11 | 89668182220 |
| 12 | 1305109502496 |
| 13 | 19138260194422 |
| 14 | 282441672732656 |
| 15 | 4191287776164504 |
| 16 | 62496081197436736 |
| 17 | 935823746406530603 |
| 18 | 14065763582458332888 |
| 19 | 212122153814497767004 |
| 20 | 3208590886304243284640 |
[0,1,8,84,992,12514,164688,2232200,30920128, 435506703,6215660600,89668182220,1305109502496, 19138260194422,282441672732656,4191287776164504, 62496081197436736,935823746406530603, 14065763582458332888,212122153814497767004, 3208590886304243284640] |