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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 40 |
| 3 | 2240 |
| 4 | 246400 |
| 5 | 44844800 |
| 6 | 12197785600 |
| 7 | 4635158528000 |
| 8 | 2345390215168000 |
| 9 | 1524503639859200000 |
| 10 | 1237896955565670400000 |
| 11 | 1227993779921145036800000 |
| 12 | 1461312598106162593792000000 |
| 13 | 2054605512937264606871552000000 |
[1,2,40,2240,246400,44844800,12197785600, 4635158528000,2345390215168000, 1524503639859200000,1237896955565670400000, 1227993779921145036800000, 1461312598106162593792000000, 2054605512937264606871552000000] |