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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 20 |
| 3 | 210 |
| 4 | 2460 |
| 5 | 31122 |
| 6 | 410378 |
| 7 | 5575682 |
| 8 | 77445152 |
| 9 | 1093987598 |
| 10 | 15660579168 |
| 11 | 226608224226 |
| 12 | 3308255447206 |
| 13 | 48658330768786 |
| 14 | 720224064591558 |
| 15 | 10718841444208526 |
| 16 | 160283814975116386 |
| 17 | 2406806389622598056 |
| 18 | 36273856567768931782 |
| 19 | 548495166665709003794 |
| 20 | 8318227159058988730096 |
[2,20,210,2460,31122,410378,5575682,77445152, 1093987598,15660579168,226608224226,3308255447206, 48658330768786,720224064591558,10718841444208526, 160283814975116386,2406806389622598056, 36273856567768931782,548495166665709003794, 8318227159058988730096] |