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| n | a(n) |
|---|---|
| 6 | 1 |
| 7 | 21 |
| 8 | 276 |
| 9 | 2925 |
| 10 | 27405 |
| 11 | 237336 |
| 12 | 1947792 |
| 13 | 15380937 |
| 14 | 118030185 |
| 15 | 886163135 |
| 16 | 6540715896 |
| 17 | 47626016970 |
| 18 | 343006888770 |
| 19 | 2448296039700 |
| 20 | 17345898649800 |
| 21 | 122131734269895 |
| 22 | 855420636763836 |
| 23 | 5964720367660956 |
[1,21,276,2925,27405,237336,1947792,15380937, 118030185,886163135,6540715896,47626016970, 343006888770,2448296039700,17345898649800, 122131734269895,855420636763836,5964720367660956] |