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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 10 |
| 6 | 30 |
| 7 | 175 |
| 8 | 1176 |
| 9 | 7084 |
| 10 | 42120 |
| 11 | 286605 |
| 12 | 2270180 |
| 13 | 19213766 |
| 14 | 166326524 |
| 15 | 1497096055 |
| 16 | 14374680880 |
| 17 | 147259920760 |
| 18 | 1582837679056 |
| 19 | 17659771122969 |
| 20 | 204674606377140 |
| 21 | 2473357218561250 |
| 22 | 31148510170120420 |
| 23 | 407154732691440811 |
| 24 | 5504706823227724904 |
[1,0,0,1,4,10,30,175,1176,7084,42120,286605, 2270180,19213766,166326524,1497096055,14374680880, 147259920760,1582837679056,17659771122969, 204674606377140,2473357218561250, 31148510170120420,407154732691440811, 5504706823227724904] |