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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 35 |
| 5 | 168 |
| 6 | 967 |
| 7 | 6538 |
| 8 | 50831 |
| 9 | 446919 |
| 10 | 4383861 |
| 11 | 47451921 |
| 12 | 561715093 |
| 13 | 7217604520 |
| 14 | 100031995789 |
| 15 | 1487319385140 |
| 16 | 23613262336093 |
| 17 | 398673670050021 |
| 18 | 7132188802005991 |
| 19 | 134766129577134553 |
| 20 | 2681929390235577831 |
[1,1,3,9,35,168,967,6538,50831,446919,4383861, 47451921,561715093,7217604520,100031995789, 1487319385140,23613262336093,398673670050021, 7132188802005991,134766129577134553, 2681929390235577831] |