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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 15 |
| 3 | 210 |
| 4 | 2926 |
| 5 | 40755 |
| 6 | 567645 |
| 7 | 7906276 |
| 8 | 110120220 |
| 9 | 1533776805 |
| 10 | 21362755051 |
| 11 | 297544793910 |
| 12 | 4144264359690 |
| 13 | 57722156241751 |
| 14 | 803965923024825 |
| 15 | 11197800766105800 |
| 16 | 155965244802456376 |
| 17 | 2172315626468283465 |
| 18 | 30256453525753512135 |
| 19 | 421418033734080886426 |
[0,1,15,210,2926,40755,567645,7906276,110120220, 1533776805,21362755051,297544793910,4144264359690, 57722156241751,803965923024825,11197800766105800, 155965244802456376,2172315626468283465, 30256453525753512135,421418033734080886426] |