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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 7 |
| 4 | 52 |
| 5 | 411 |
| 6 | 4440 |
| 7 | 73886 |
| 8 | 2128608 |
| 9 | 111533208 |
| 10 | 10812478194 |
| 11 | 1945437194308 |
| 12 | 650378721118910 |
| 13 | 404749938336301313 |
| 14 | 470163239887698682289 |
| 15 | 1022592854829028310302180 |
| 16 | 4177826139658552046624979658 |
| 17 | 32163829440870460348768017832607 |
| 18 | 468021728889827507080865185809438918 |
[0,0,1,7,52,411,4440,73886,2128608,111533208, 10812478194,1945437194308,650378721118910, 404749938336301313,470163239887698682289, 1022592854829028310302180, 4177826139658552046624979658, 32163829440870460348768017832607, 468021728889827507080865185809438918] |