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| n | a(n) |
|---|---|
| 3 | 0 |
| 4 | 0 |
| 5 | 720 |
| 6 | 0 |
| 7 | 0 |
| 8 | 3600 |
| 9 | 2400 |
| 10 | 4320 |
| 11 | 28800 |
| 12 | 35400 |
| 13 | 64800 |
| 14 | 284400 |
| 15 | 540000 |
| 16 | 1139400 |
| 17 | 3708000 |
| 18 | 8557200 |
| 19 | 19677600 |
| 20 | 55725120 |
| 21 | 140359200 |
| 22 | 346456800 |
| 23 | 935942400 |
| 24 | 2442469200 |
| 25 | 6282571680 |
[0,0,720,0,0,3600,2400,4320,28800,35400,64800, 284400,540000,1139400,3708000,8557200,19677600, 55725120,140359200,346456800,935942400,2442469200, 6282571680] |