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| n | a(n) |
|---|---|
| 4 | 1 |
| 5 | 10 |
| 6 | 120 |
| 7 | 1540 |
| 8 | 21490 |
| 9 | 326970 |
| 10 | 5402250 |
| 11 | 96500250 |
| 12 | 1855334250 |
| 13 | 38228190000 |
| 14 | 840776937000 |
| 15 | 19666511865000 |
| 16 | 487617137007000 |
| 17 | 12776791730703000 |
| 18 | 352825452012033000 |
| 19 | 10242418813814187000 |
| 20 | 311854958169459705000 |
| 21 | 9937942309809373860000 |
| 22 | 330821844137019184950000 |
[1,10,120,1540,21490,326970,5402250,96500250, 1855334250,38228190000,840776937000, 19666511865000,487617137007000,12776791730703000, 352825452012033000,10242418813814187000, 311854958169459705000,9937942309809373860000, 330821844137019184950000] |