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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 60 |
| 6 | 240 |
| 7 | 1260 |
| 8 | 169344 |
| 9 | 1693440 |
| 10 | 17150400 |
| 11 | 187941600 |
| 12 | 12778698240 |
| 13 | 271809457920 |
| 14 | 5031211086720 |
| 15 | 91848556800000 |
| 16 | 4643532967772160 |
| 17 | 154079136039628800 |
| 18 | 4367731446302515200 |
| 19 | 117143657916761548800 |
| 20 | 5457792037686441984000 |
[1,0,0,0,24,60,240,1260,169344,1693440,17150400, 187941600,12778698240,271809457920,5031211086720, 91848556800000,4643532967772160, 154079136039628800,4367731446302515200, 117143657916761548800,5457792037686441984000] |