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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 24 |
| 5 | 184 |
| 6 | 1911 |
| 7 | 24252 |
| 8 | 362199 |
| 9 | 6162080 |
| 10 | 117342912 |
| 11 | 2469791336 |
| 12 | 56919388745 |
| 13 | 1425435420600 |
| 14 | 38543562608825 |
| 15 | 1119188034056244 |
| 16 | 34733368101580440 |
| 17 | 1147320305439301344 |
| 18 | 40190943859500501151 |
| 19 | 1488212241729974297796 |
| 20 | 58080468361734193793551 |
[1,0,1,4,24,184,1911,24252,362199,6162080, 117342912,2469791336,56919388745,1425435420600, 38543562608825,1119188034056244,34733368101580440, 1147320305439301344,40190943859500501151, 1488212241729974297796,58080468361734193793551] |