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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 140 |
| 6 | 870 |
| 7 | 5922 |
| 8 | 45416 |
| 9 | 381096 |
| 10 | 3442410 |
| 11 | 33382910 |
| 12 | 345803172 |
| 13 | 3801763836 |
| 14 | 44156760830 |
| 15 | 539962736250 |
| 16 | 6929042527920 |
| 17 | 93032248209872 |
| 18 | 1303556965679826 |
| 19 | 19018807375195638 |
| 20 | 288341417011487420 |
| 21 | 4534168069704168420 |
| 22 | 73829219253218066022 |
| 23 | 1242905562198878544626 |
[1,0,2,6,24,140,870,5922,45416,381096,3442410, 33382910,345803172,3801763836,44156760830, 539962736250,6929042527920,93032248209872, 1303556965679826,19018807375195638, 288341417011487420,4534168069704168420, 73829219253218066022,1242905562198878544626] |