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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 120 |
| 7 | 14400 |
| 8 | 0 |
| 9 | 360000 |
| 10 | 0 |
| 11 | 1440000 |
| 12 | 0 |
| 13 | 1440000 |
| 14 | 0 |
| 15 | 360000 |
| 16 | 0 |
| 17 | 14400 |
| 18 | 3891456000 |
| 19 | 26179200000 |
| 20 | 83980800000 |
| 21 | 171676800000 |
| 22 | 249091200000 |
| 23 | 270869184000 |
| 24 | 226368000000 |
| 25 | 150465600000 |
| 26 | 77760000000 |
[1,0,0,0,0,0,120,14400,0,360000,0,1440000,0, 1440000,0,360000,0,14400,3891456000,26179200000, 83980800000,171676800000,249091200000, 270869184000,226368000000,150465600000, 77760000000] |