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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 72 |
| 4 | 1776 |
| 5 | 89280 |
| 6 | 9065472 |
| 7 | 1850148864 |
| 8 | 757046525952 |
| 9 | 620298979246080 |
| 10 | 1017126921430892544 |
| 11 | 3336658943759213395968 |
| 12 | 21894988380633154342354944 |
| 13 | 287369531352172835754234347520 |
| 14 | 7543680108676972971562235527692288 |
[1,1,6,72,1776,89280,9065472,1850148864, 757046525952,620298979246080,1017126921430892544, 3336658943759213395968,21894988380633154342354944, 287369531352172835754234347520, 7543680108676972971562235527692288] |