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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 12 |
| 5 | 312 |
| 6 | 9600 |
| 7 | 416880 |
| 8 | 23879520 |
| 9 | 1749363840 |
| 10 | 159591720960 |
| 11 | 17747520940800 |
| 12 | 2363738855385600 |
| 13 | 371511874881100800 |
| 14 | 68045361697964851200 |
| 15 | 14367543450324474009600 |
| 16 | 3464541314885011705344000 |
| 17 | 946263209467217020194816000 |
| 18 | 290616691739323132839591936000 |
[0,0,2,12,312,9600,416880,23879520,1749363840, 159591720960,17747520940800,2363738855385600, 371511874881100800,68045361697964851200, 14367543450324474009600,3464541314885011705344000, 946263209467217020194816000, 290616691739323132839591936000] |