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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 36 |
| 3 | 324 |
| 4 | 3888 |
| 5 | 58320 |
| 6 | 1049760 |
| 7 | 22044960 |
| 8 | 529079040 |
| 9 | 14285134080 |
| 10 | 428554022400 |
| 11 | 14142282739200 |
| 12 | 509122178611200 |
| 13 | 19855764965836800 |
| 14 | 833942128565145600 |
| 15 | 37527395785431552000 |
| 16 | 1801314997700714496000 |
| 17 | 91867064882736439296000 |
| 18 | 4960821503667767721984000 |
[1,6,36,324,3888,58320,1049760,22044960,529079040, 14285134080,428554022400,14142282739200, 509122178611200,19855764965836800, 833942128565145600,37527395785431552000, 1801314997700714496000,91867064882736439296000, 4960821503667767721984000] |