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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 21 |
| 5 | 60 |
| 6 | 285 |
| 7 | 2170 |
| 8 | 12873 |
| 9 | 54936 |
| 10 | 391065 |
| 11 | 4881998 |
| 12 | 33969309 |
| 13 | 28359188 |
| 14 | 826179445 |
| 15 | 48496348290 |
| 16 | 328705747217 |
| 17 | -5928717037136 |
| 18 | -26909518872399 |
| 19 | 2320514677184022 |
| 20 | 14213386673919397 |
[1,0,1,6,21,60,285,2170,12873,54936,391065, 4881998,33969309,28359188,826179445,48496348290, 328705747217,-5928717037136,-26909518872399, 2320514677184022,14213386673919397] |