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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 720 |
| 8 | 0 |
| 9 | 0 |
| 10 | 172800 |
| 11 | 3628800 |
| 12 | 0 |
| 13 | 0 |
| 14 | 2641766400 |
| 15 | 87178291200 |
| 16 | 0 |
| 17 | 0 |
| 18 | 225422681702400 |
| 19 | 6402373705728000 |
| 20 | 0 |
| 21 | 221172909834240000 |
| 22 | 30424079849619456000 |
| 23 | 1124000727777607680000 |
| 24 | 0 |
| 25 | 49241936645495193600000 |
| 26 | 11321261082950211993600000 |
[1,0,0,2,0,0,0,720,0,0,172800,3628800,0,0, 2641766400,87178291200,0,0,225422681702400, 6402373705728000,0,221172909834240000, 30424079849619456000,1124000727777607680000,0, 49241936645495193600000, 11321261082950211993600000] |