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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 20 |
| 6 | 300 |
| 7 | 4200 |
| 8 | 58835 |
| 9 | 849240 |
| 10 | 12814200 |
| 11 | 203742000 |
| 12 | 3430355775 |
| 13 | 61363001700 |
| 14 | 1168815948300 |
| 15 | 23734579869000 |
| 16 | 513878948207625 |
| 17 | 11850279026586000 |
| 18 | 290440507342986000 |
| 19 | 7543064638441332000 |
| 20 | 206860683821114948625 |
| 21 | 5968372055889205462500 |
[1,0,0,0,1,20,300,4200,58835,849240,12814200, 203742000,3430355775,61363001700,1168815948300, 23734579869000,513878948207625,11850279026586000, 290440507342986000,7543064638441332000, 206860683821114948625,5968372055889205462500] |