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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
| 4 | -3 |
| 5 | 0 |
| 6 | 45 |
| 7 | 504 |
| 8 | 2457 |
| 9 | 24384 |
| 10 | 161625 |
| 11 | 2375296 |
| 12 | 20549397 |
| 13 | 338479232 |
| 14 | 3457938757 |
| 15 | 64501554688 |
| 16 | 772773915313 |
| 17 | 16130341302272 |
| 18 | 221864504883633 |
| 19 | 5112670099460096 |
| 20 | 79479234590193325 |
| 21 | 2003580047549120512 |
[1,1,1,0,-3,0,45,504,2457,24384,161625,2375296, 20549397,338479232,3457938757,64501554688, 772773915313,16130341302272,221864504883633, 5112670099460096,79479234590193325, 2003580047549120512] |