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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 72 |
| 3 | 1560 |
| 4 | 11760 |
| 5 | 177144 |
| 6 | 482664 |
| 7 | 2413728 |
| 8 | 4704552 |
| 9 | 14803536 |
| 10 | 59482248 |
| 11 | 88750272 |
| 12 | 256572504 |
| 13 | 475010256 |
| 14 | 632136120 |
| 15 | 1077921312 |
| 16 | 2216435832 |
| 17 | 4218053016 |
| 18 | 5152037064 |
| 19 | 9045837768 |
| 20 | 12810027888 |
| 21 | 15133422096 |
| 22 | 24308744928 |
[6,72,1560,11760,177144,482664,2413728,4704552, 14803536,59482248,88750272,256572504,475010256, 632136120,1077921312,2216435832,4218053016, 5152037064,9045837768,12810027888,15133422096, 24308744928] |