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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 24 |
| 3 | 253 |
| 4 | 3045 |
| 5 | 39627 |
| 6 | 543004 |
| 7 | 7718340 |
| 8 | 112752783 |
| 9 | 1682460520 |
| 10 | 25533901536 |
| 11 | 392912889915 |
| 12 | 6116090678334 |
| 13 | 96133810101609 |
| 14 | 1523687678528400 |
| 15 | 24324750346691480 |
| 16 | 390786855500604195 |
| 17 | 6313161418594235271 |
| 18 | 102494297789621214400 |
| 19 | 1671366110239940499000 |
[1,3,24,253,3045,39627,543004,7718340,112752783, 1682460520,25533901536,392912889915,6116090678334, 96133810101609,1523687678528400,24324750346691480, 390786855500604195,6313161418594235271, 102494297789621214400,1671366110239940499000] |