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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 35 |
| 6 | 295 |
| 7 | 3304 |
| 8 | 42112 |
| 9 | 599724 |
| 10 | 9657330 |
| 11 | 174222576 |
| 12 | 3464835726 |
| 13 | 75208002792 |
| 14 | 1771121398956 |
| 15 | 44998593873024 |
| 16 | 1226723273550720 |
| 17 | 35714547582173280 |
| 18 | 1106012915718532920 |
| 19 | 36304411160854523520 |
| 20 | 1259105580819317636280 |
| 21 | 46007354360033491345920 |
[1,0,0,1,6,35,295,3304,42112,599724,9657330, 174222576,3464835726,75208002792,1771121398956, 44998593873024,1226723273550720,35714547582173280, 1106012915718532920,36304411160854523520, 1259105580819317636280,46007354360033491345920] |