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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 10 |
| 5 | 74 |
| 6 | 216 |
| 7 | 2316 |
| 8 | 8688 |
| 9 | 128880 |
| 10 | 581760 |
| 11 | 11406240 |
| 12 | 59667840 |
| 13 | 1482693120 |
| 14 | 8782905600 |
| 15 | 266800262400 |
| 16 | 1762116249600 |
| 17 | 63536485017600 |
| 18 | 462613126348800 |
| 19 | 19342202181120000 |
| 20 | 153884245616640000 |
| 21 | 7325057766297600000 |
[1,1,5,10,74,216,2316,8688,128880,581760,11406240, 59667840,1482693120,8782905600,266800262400, 1762116249600,63536485017600,462613126348800, 19342202181120000,153884245616640000, 7325057766297600000] |