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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 15 |
| 5 | 222 |
| 6 | 3760 |
| 7 | 73755 |
| 8 | 1657845 |
| 9 | 42143500 |
| 10 | 1197163134 |
| 11 | 37613828070 |
| 12 | 1295741321875 |
| 13 | 48577055308320 |
| 14 | 1969293264235635 |
| 15 | 85852853154670693 |
| 16 | 4005625283891276535 |
| 17 | 199166987259400191480 |
| 18 | 10513996906985414443720 |
| 19 | 587316057411626070658200 |
| 20 | 34612299496604684775762261 |
[1,0,0,1,15,222,3760,73755,1657845,42143500, 1197163134,37613828070,1295741321875, 48577055308320,1969293264235635,85852853154670693, 4005625283891276535,199166987259400191480, 10513996906985414443720,587316057411626070658200, 34612299496604684775762261] |