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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 36 |
| 4 | 432 |
| 5 | 3660 |
| 6 | 27000 |
| 7 | 185556 |
| 8 | 1223712 |
| 9 | 7862940 |
| 10 | 49653000 |
| 11 | 309776676 |
| 12 | 1915868592 |
| 13 | 11772890220 |
| 14 | 71992229400 |
| 15 | 438593697396 |
| 16 | 2664227115072 |
| 17 | 16146540253500 |
| 18 | 97676540188200 |
| 19 | 590011376299716 |
| 20 | 3559691497843152 |
| 21 | 21455715437760780 |
| 22 | 129219925869401400 |
[0,0,0,36,432,3660,27000,185556,1223712,7862940, 49653000,309776676,1915868592,11772890220, 71992229400,438593697396,2664227115072, 16146540253500,97676540188200,590011376299716, 3559691497843152,21455715437760780, 129219925869401400] |