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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 24 |
| 3 | 120 |
| 4 | 576 |
| 5 | 2760 |
| 6 | 12984 |
| 7 | 60984 |
| 8 | 285408 |
| 9 | 1333800 |
| 10 | 6233160 |
| 11 | 29160384 |
| 12 | 136266336 |
| 13 | 637801008 |
| 14 | 2981648544 |
| 15 | 13958155920 |
| 16 | 65277740160 |
| 17 | 305608333056 |
| 18 | 1429708907808 |
| 19 | 6693530115984 |
| 20 | 31322446230480 |
| 21 | 146644481840472 |
| 22 | 686366895112272 |
| 23 | 3213444320539704 |
| 24 | 15042778262399904 |
[6,24,120,576,2760,12984,60984,285408,1333800, 6233160,29160384,136266336,637801008,2981648544, 13958155920,65277740160,305608333056, 1429708907808,6693530115984,31322446230480, 146644481840472,686366895112272,3213444320539704, 15042778262399904] |