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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 20 |
| 4 | 64 |
| 5 | 1668 |
| 6 | 27712 |
| 7 | 355279 |
| 8 | 779264 |
| 9 | 170190707 |
| 10 | 6100448256 |
| 11 | 159424073982 |
| 12 | 2545667031040 |
| 13 | 239361355053790 |
| 14 | 812743283245056 |
| 15 | 58702956893404802 |
| 16 | 17949710147773530112 |
| 17 | 488189490082385976772 |
| 18 | 38768887410023899070464 |
| 19 | 313775221076492698014434 |
| 20 | 11531764219557396646723584 |
[0,0,0,20,64,1668,27712,355279,779264,170190707, 6100448256,159424073982,2545667031040, 239361355053790,812743283245056,58702956893404802, 17949710147773530112,488189490082385976772, 38768887410023899070464,313775221076492698014434, 11531764219557396646723584] |