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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 48 |
| 5 | 440 |
| 6 | 5310 |
| 7 | 77952 |
| 8 | 1356152 |
| 9 | 27284112 |
| 10 | 623393370 |
| 11 | 15946253840 |
| 12 | 451464791052 |
| 13 | 14014830400584 |
| 14 | 473330219980982 |
| 15 | 17278004243854200 |
| 16 | 677844684489863760 |
| 17 | 28441920741699231392 |
| 18 | 1270962028978738313778 |
| 19 | 60259311813834246030048 |
| 20 | 3021271708308614076699380 |
[1,0,2,6,48,440,5310,77952,1356152,27284112, 623393370,15946253840,451464791052,14014830400584, 473330219980982,17278004243854200, 677844684489863760,28441920741699231392, 1270962028978738313778,60259311813834246030048, 3021271708308614076699380] |