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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 6 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 2520 |
| 9 | 40320 |
| 10 | 0 |
| 11 | 0 |
| 12 | 7484400 |
| 13 | 345945600 |
| 14 | 6227020800 |
| 15 | 0 |
| 16 | 81729648000 |
| 17 | 7410154752000 |
| 18 | 307697854464000 |
| 19 | 6402373705728000 |
| 20 | 2375880867360000 |
| 21 | 354798209525760000 |
| 22 | 25460995321681920000 |
| 23 | 1090665702016450560000 |
| 24 | 26003493399464380800000 |
[1,0,0,0,6,0,0,0,2520,40320,0,0,7484400,345945600, 6227020800,0,81729648000,7410154752000, 307697854464000,6402373705728000,2375880867360000, 354798209525760000,25460995321681920000, 1090665702016450560000,26003493399464380800000] |