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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 5 |
| 6 | 15 |
| 7 | 40 |
| 8 | 97 |
| 9 | 237 |
| 10 | 571 |
| 11 | 1385 |
| 12 | 3263 |
| 13 | 7618 |
| 14 | 17580 |
| 15 | 40146 |
| 16 | 90962 |
| 17 | 204618 |
| 18 | 457446 |
| 19 | 1016494 |
| 20 | 2247000 |
| 21 | 4943400 |
| 22 | 10828248 |
| 23 | 23625120 |
| 24 | 51358776 |
| 25 | 111277576 |
| 26 | 240359368 |
| 27 | 517697136 |
| 28 | 1112090144 |
| 29 | 2383049792 |
| 30 | 5094795600 |
| 31 | 10868896688 |
| 32 | 23140232368 |
| 33 | 49172993152 |
[0,0,0,0,2,5,15,40,97,237,571,1385,3263,7618, 17580,40146,90962,204618,457446,1016494,2247000, 4943400,10828248,23625120,51358776,111277576, 240359368,517697136,1112090144,2383049792, 5094795600,10868896688,23140232368,49172993152] |