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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 1860 |
| 3 | 297200 |
| 4 | 60871300 |
| 5 | 14367744720 |
| 6 | 3718394156400 |
| 7 | 1026608414145600 |
| 8 | 297348703692826500 |
| 9 | 89365729945562642000 |
| 10 | 27658131940039664137360 |
| 11 | 8766913970029589057611200 |
| 12 | 2834492178580299130305958000 |
| 13 | 931874436031756882451601080000 |
| 14 | 310768686646948895430510472680000 |
[1,20,1860,297200,60871300,14367744720, 3718394156400,1026608414145600,297348703692826500, 89365729945562642000,27658131940039664137360, 8766913970029589057611200, 2834492178580299130305958000, 931874436031756882451601080000, 310768686646948895430510472680000] |