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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 3 |
| 3 | 6 |
| 4 | 81 |
| 5 | 540 |
| 6 | 7155 |
| 7 | 85050 |
| 8 | 1346625 |
| 9 | 22339800 |
| 10 | 431331075 |
| 11 | 9004668750 |
| 12 | 208178118225 |
| 13 | 5199538043700 |
| 14 | 140664514065075 |
| 15 | 4080315642653250 |
| 16 | 126613733680058625 |
| 17 | 4180226398201854000 |
| 18 | 146399020309066399875 |
| 19 | 5419213146765629961750 |
| 20 | 211446723837565171580625 |
[1,0,3,6,81,540,7155,85050,1346625,22339800, 431331075,9004668750,208178118225,5199538043700, 140664514065075,4080315642653250, 126613733680058625,4180226398201854000, 146399020309066399875,5419213146765629961750, 211446723837565171580625] |