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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 9 |
| 3 | 60 |
| 4 | 504 |
| 5 | 6336 |
| 6 | 89856 |
| 7 | 1645056 |
| 8 | 33094656 |
| 9 | 801239040 |
| 10 | 24246190080 |
| 11 | 777550233600 |
| 12 | 29697402470400 |
| 13 | 1250501433753600 |
| 14 | 55083063155097600 |
| 15 | 2649111037319577600 |
| 16 | 143390180403000115200 |
| 17 | 8619643674791667302400 |
| 18 | 534710099148093259776000 |
| 19 | 36412881178052121329664000 |
[2,9,60,504,6336,89856,1645056,33094656,801239040, 24246190080,777550233600,29697402470400, 1250501433753600,55083063155097600, 2649111037319577600,143390180403000115200, 8619643674791667302400,534710099148093259776000, 36412881178052121329664000] |