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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 4 |
| 4 | 6 |
| 5 | 40 |
| 6 | 150 |
| 7 | 832 |
| 8 | 4494 |
| 9 | 27496 |
| 10 | 178278 |
| 11 | 1240720 |
| 12 | 9159678 |
| 13 | 71523448 |
| 14 | 588049878 |
| 15 | 5073746464 |
| 16 | 45800173038 |
| 17 | 431400176008 |
| 18 | 4230061102662 |
| 19 | 43087882883248 |
| 20 | 455079854567646 |
| 21 | 4975136823055768 |
| 22 | 56212975652894646 |
| 23 | 655496634896272960 |
| 24 | 7878552380411524302 |
[0,1,0,4,6,40,150,832,4494,27496,178278,1240720, 9159678,71523448,588049878,5073746464,45800173038, 431400176008,4230061102662,43087882883248, 455079854567646,4975136823055768, 56212975652894646,655496634896272960, 7878552380411524302] |