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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 8 |
| 3 | 36 |
| 4 | 180 |
| 5 | 1080 |
| 6 | 7560 |
| 7 | 60480 |
| 8 | 524160 |
| 9 | 5241600 |
| 10 | 56609280 |
| 11 | 670602240 |
| 12 | 8622028800 |
| 13 | 118879488000 |
| 14 | 1793381990400 |
| 15 | 28158588057600 |
| 16 | 474249904128000 |
| 17 | 8447576417280000 |
| 18 | 159659194286592000 |
| 19 | 3162772610629632000 |
| 20 | 66117689869271040000 |
| 21 | 1445143792856924160000 |
[2,8,36,180,1080,7560,60480,524160,5241600, 56609280,670602240,8622028800,118879488000, 1793381990400,28158588057600,474249904128000, 8447576417280000,159659194286592000, 3162772610629632000,66117689869271040000, 1445143792856924160000] |