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| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 12 |
| 4 | 84 |
| 5 | 640 |
| 6 | 5236 |
| 7 | 45164 |
| 8 | 406012 |
| 9 | 3772008 |
| 10 | 35994184 |
| 11 | 351173328 |
| 12 | 3490681428 |
| 13 | 35253449296 |
| 14 | 360946635312 |
| 15 | 3739935635756 |
| 16 | 39159200588780 |
| 17 | 413836299216608 |
| 18 | 4409705753032648 |
| 19 | 47337525317450816 |
| 20 | 511563350415103008 |
[2,12,84,640,5236,45164,406012,3772008,35994184, 351173328,3490681428,35253449296,360946635312, 3739935635756,39159200588780,413836299216608, 4409705753032648,47337525317450816, 511563350415103008] |