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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 157 |
| 5 | 1800 |
| 6 | 25551 |
| 7 | 432376 |
| 8 | 8494809 |
| 9 | 190029888 |
| 10 | 4768313275 |
| 11 | 132626098176 |
| 12 | 4049755214517 |
| 13 | 134677876657792 |
| 14 | 4845193429684167 |
| 15 | 187490897290080000 |
| 16 | 7765153170076158001 |
| 17 | 342721890859339812864 |
| 18 | 16058392049508837366771 |
| 19 | 796093438190851834236928 |
[1,1,3,18,157,1800,25551,432376,8494809,190029888, 4768313275,132626098176,4049755214517, 134677876657792,4845193429684167, 187490897290080000,7765153170076158001, 342721890859339812864,16058392049508837366771, 796093438190851834236928] |