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| n | a(n) |
|---|---|
| 1 | 408 |
| 2 | 2628 |
| 3 | 16848 |
| 4 | 109224 |
| 5 | 704160 |
| 6 | 4594320 |
| 7 | 29782080 |
| 8 | 195532704 |
| 9 | 1274237568 |
| 10 | 8416415808 |
| 11 | 55124437248 |
| 12 | 366185867904 |
| 13 | 2409750673920 |
| 14 | 16093719394560 |
| 15 | 106373608473600 |
| 16 | 713965515692544 |
| 17 | 4738136283260928 |
| 18 | 31947371388453888 |
[408,2628,16848,109224,704160,4594320,29782080, 195532704,1274237568,8416415808,55124437248, 366185867904,2409750673920,16093719394560, 106373608473600,713965515692544,4738136283260928, 31947371388453888] |