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| n | a(n) |
|---|---|
| 5 | 1 |
| 6 | 4 |
| 7 | 10 |
| 8 | 19 |
| 9 | 40 |
| 10 | 120 |
| 11 | 445 |
| 12 | 2107 |
| 13 | 10099 |
| 14 | 50833 |
| 15 | 296830 |
| 16 | 2080084 |
| 17 | 17252149 |
| 18 | 164656985 |
| 19 | 1767665953 |
| 20 | 21481633518 |
| 21 | 300312864497 |
[1,4,10,19,40,120,445,2107,10099,50833,296830, 2080084,17252149,164656985,1767665953,21481633518, 300312864497] |