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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 20 |
| 5 | 12798 |
| 6 | 763144 |
| 7 | 15516804 |
| 8 | 170842828 |
| 9 | 1264750240 |
| 10 | 7084450248 |
| 11 | 32251861624 |
| 12 | 125030824732 |
| 13 | 426265242412 |
| 14 | 1308045124808 |
| 15 | 3675893768908 |
| 16 | 9586626461484 |
| 17 | 23445303141400 |
| 18 | 54219244028296 |
| 19 | 119372323892736 |
| 20 | 251614892723068 |
| 21 | 510130577706724 |
| 22 | 998740710435208 |
[0,0,0,20,12798,763144,15516804,170842828, 1264750240,7084450248,32251861624,125030824732, 426265242412,1308045124808,3675893768908, 9586626461484,23445303141400,54219244028296, 119372323892736,251614892723068,510130577706724, 998740710435208] |