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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 6 |
| 2 | 15 |
| 3 | 105 |
| 4 | 105 |
| 5 | 231 |
| 6 | 15015 |
| 7 | 2145 |
| 8 | 36465 |
| 9 | 969969 |
| 10 | 4849845 |
| 11 | 10140585 |
| 12 | 10140585 |
| 13 | 22287 |
| 14 | 3231615 |
| 15 | 7713865005 |
| 16 | 7713865005 |
| 17 | 90751353 |
| 18 | 218257003965 |
| 19 | 1641030105 |
| 20 | 67282234305 |
| 21 | 368217318651 |
| 22 | 1841086593255 |
[2,6,15,105,105,231,15015,2145,36465,969969, 4849845,10140585,10140585,22287,3231615, 7713865005,7713865005,90751353,218257003965, 1641030105,67282234305,368217318651,1841086593255] |