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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 270 |
| 3 | 14280 |
| 4 | 1027950 |
| 5 | 49945896 |
| 6 | 3576428856 |
| 7 | 206746398144 |
| 8 | 14538815734014 |
| 9 | 856120482145500 |
| 10 | 57732481295380320 |
| 11 | 3504640795033499160 |
| 12 | 243836930413853027160 |
| 13 | 14665028066155264295400 |
| 14 | 977424087385506563672160 |
| 15 | 61042393779786411602842080 |
[1,6,270,14280,1027950,49945896,3576428856, 206746398144,14538815734014,856120482145500, 57732481295380320,3504640795033499160, 243836930413853027160,14665028066155264295400, 977424087385506563672160, 61042393779786411602842080] |