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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 20 |
| 3 | 640 |
| 4 | 78080 |
| 5 | 37847040 |
| 6 | 74189111296 |
| 7 | 589682903613440 |
| 8 | 18955380356036952064 |
| 9 | 2455824622368881511497728 |
| 10 | 1278825951842748707166092263424 |
| 11 | 2671459568763422966186162922297753600 |
[1,2,20,640,78080,37847040,74189111296, 589682903613440,18955380356036952064, 2455824622368881511497728, 1278825951842748707166092263424, 2671459568763422966186162922297753600] |