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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 609250 |
| 4 | 3721431625 |
| 5 | 12129909700200 |
| 6 | 31147299733286500 |
| 7 | 71578406022880761750 |
| 8 | 154990541752961568418125 |
| 9 | 324064464310279585657008750 |
| 10 | 662863774391414096742406576300 |
| 11 | 1336442091735463067608016312923750 |
| 12 | 2668147157687867719032781403203942875 |
| 13 | 5290387928421738826068606777043538125500 |
[0,0,609250,3721431625,12129909700200, 31147299733286500,71578406022880761750, 154990541752961568418125, 324064464310279585657008750, 662863774391414096742406576300, 1336442091735463067608016312923750, 2668147157687867719032781403203942875, 5290387928421738826068606777043538125500] |